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Quellcode-Bibliothek fts5.c

Interaktion und
PortierbarkeitC

/*
** This, the "fts5.c" source file, is a composite file that is itself
** assembled from the following files:
**
** fts5.h
** fts5Int.h
** fts5parse.h <--- Generated from fts5parse.y by Lemon
** fts5parse.c <--- Generated from fts5parse.y by Lemon
** fts5_aux.c
** fts5_buffer.c
** fts5_config.c
** fts5_expr.c
** fts5_hash.c
** fts5_index.c
** fts5_main.c
** fts5_storage.c
** fts5_tokenize.c
** fts5_unicode2.c
** fts5_varint.c
** fts5_vocab.c
*/
#if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS5)

#if !defined(NDEBUG) && !defined(SQLITE_DEBUG)
# define NDEBUG 1
#endif
#if defined(NDEBUG) && defined(SQLITE_DEBUG)
# undef NDEBUG
#endif

#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif
#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif
#line 1 "fts5.h"
/*
** 2014 May 31
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** Interfaces to extend FTS5. Using the interfaces defined in this file,
** FTS5 may be extended with:
**
** * custom tokenizers, and
** * custom auxiliary functions.
*/

#ifndef _FTS5_H
#define _FTS5_H

#include "sqlite3.h"

#ifdef __cplusplus
extern "C" {
#endif

/*************************************************************************
** CUSTOM AUXILIARY FUNCTIONS
**
** Virtual table implementations may overload SQL functions by implementing
** the sqlite3_module.xFindFunction() method.
*/

typedef struct Fts5ExtensionApi Fts5ExtensionApi;
typedef struct Fts5Context Fts5Context;
typedef struct Fts5PhraseIter Fts5PhraseIter;

typedef void (*fts5_extension_function)(
 const Fts5ExtensionApi *pApi, /* API offered by current FTS version */
 Fts5Context *pFts, /* First arg to pass to pApi functions */
 sqlite3_context *pCtx, /* Context for returning result/error */
 int nVal, /* Number of values in apVal[] array */
 sqlite3_value **apVal /* Array of trailing arguments */
);

struct Fts5PhraseIter {
 const unsigned char *a;
 const unsigned char *b;
};

/*
** EXTENSION API FUNCTIONS
**
** xUserData(pFts):
** Return a copy of the pUserData pointer passed to the xCreateFunction()
** API when the extension function was registered.
**
** xColumnTotalSize(pFts, iCol, pnToken):
** If parameter iCol is less than zero, set output variable *pnToken
** to the total number of tokens in the FTS5 table. Or, if iCol is
** non-negative but less than the number of columns in the table, return
** the total number of tokens in column iCol, considering all rows in
** the FTS5 table.
**
** If parameter iCol is greater than or equal to the number of columns
** in the table, SQLITE_RANGE is returned. Or, if an error occurs (e.g.
** an OOM condition or IO error), an appropriate SQLite error code is
** returned.
**
** xColumnCount(pFts):
** Return the number of columns in the table.
**
** xColumnSize(pFts, iCol, pnToken):
** If parameter iCol is less than zero, set output variable *pnToken
** to the total number of tokens in the current row. Or, if iCol is
** non-negative but less than the number of columns in the table, set
** *pnToken to the number of tokens in column iCol of the current row.
**
** If parameter iCol is greater than or equal to the number of columns
** in the table, SQLITE_RANGE is returned. Or, if an error occurs (e.g.
** an OOM condition or IO error), an appropriate SQLite error code is
** returned.
**
** This function may be quite inefficient if used with an FTS5 table
** created with the "columnsize=0" option.
**
** xColumnText:
** If parameter iCol is less than zero, or greater than or equal to the
** number of columns in the table, SQLITE_RANGE is returned.
**
** Otherwise, this function attempts to retrieve the text of column iCol of
** the current document. If successful, (*pz) is set to point to a buffer
** containing the text in utf-8 encoding, (*pn) is set to the size in bytes
** (not characters) of the buffer and SQLITE_OK is returned. Otherwise,
** if an error occurs, an SQLite error code is returned and the final values
** of (*pz) and (*pn) are undefined.
**
** xPhraseCount:
** Returns the number of phrases in the current query expression.
**
** xPhraseSize:
** If parameter iCol is less than zero, or greater than or equal to the
** number of phrases in the current query, as returned by xPhraseCount,
** 0 is returned. Otherwise, this function returns the number of tokens in
** phrase iPhrase of the query. Phrases are numbered starting from zero.
**
** xInstCount:
** Set *pnInst to the total number of occurrences of all phrases within
** the query within the current row. Return SQLITE_OK if successful, or
** an error code (i.e. SQLITE_NOMEM) if an error occurs.
**
** This API can be quite slow if used with an FTS5 table created with the
** "detail=none" or "detail=column" option. If the FTS5 table is created
** with either "detail=none" or "detail=column" and "content=" option
** (i.e. if it is a contentless table), then this API always returns 0.
**
** xInst:
** Query for the details of phrase match iIdx within the current row.
** Phrase matches are numbered starting from zero, so the iIdx argument
** should be greater than or equal to zero and smaller than the value
** output by xInstCount(). If iIdx is less than zero or greater than
** or equal to the value returned by xInstCount(), SQLITE_RANGE is returned.
**
** Otherwise, output parameter *piPhrase is set to the phrase number, *piCol
** to the column in which it occurs and *piOff the token offset of the
** first token of the phrase. SQLITE_OK is returned if successful, or an
** error code (i.e. SQLITE_NOMEM) if an error occurs.
**
** This API can be quite slow if used with an FTS5 table created with the
** "detail=none" or "detail=column" option.
**
** xRowid:
** Returns the rowid of the current row.
**
** xTokenize:
** Tokenize text using the tokenizer belonging to the FTS5 table.
**
** xQueryPhrase(pFts5, iPhrase, pUserData, xCallback):
** This API function is used to query the FTS table for phrase iPhrase
** of the current query. Specifically, a query equivalent to:
**
** ... FROM ftstable WHERE ftstable MATCH $p ORDER BY rowid
**
** with $p set to a phrase equivalent to the phrase iPhrase of the
** current query is executed. Any column filter that applies to
** phrase iPhrase of the current query is included in $p. For each
** row visited, the callback function passed as the fourth argument
** is invoked. The context and API objects passed to the callback
** function may be used to access the properties of each matched row.
** Invoking Api.xUserData() returns a copy of the pointer passed as
** the third argument to pUserData.
**
** If parameter iPhrase is less than zero, or greater than or equal to
** the number of phrases in the query, as returned by xPhraseCount(),
** this function returns SQLITE_RANGE.
**
** If the callback function returns any value other than SQLITE_OK, the
** query is abandoned and the xQueryPhrase function returns immediately.
** If the returned value is SQLITE_DONE, xQueryPhrase returns SQLITE_OK.
** Otherwise, the error code is propagated upwards.
**
** If the query runs to completion without incident, SQLITE_OK is returned.
** Or, if some error occurs before the query completes or is aborted by
** the callback, an SQLite error code is returned.
**
**
** xSetAuxdata(pFts5, pAux, xDelete)
**
** Save the pointer passed as the second argument as the extension function's
** "auxiliary data". The pointer may then be retrieved by the current or any
** future invocation of the same fts5 extension function made as part of
** the same MATCH query using the xGetAuxdata() API.
**
** Each extension function is allocated a single auxiliary data slot for
** each FTS query (MATCH expression). If the extension function is invoked
** more than once for a single FTS query, then all invocations share a
** single auxiliary data context.
**
** If there is already an auxiliary data pointer when this function is
** invoked, then it is replaced by the new pointer. If an xDelete callback
** was specified along with the original pointer, it is invoked at this
** point.
**
** The xDelete callback, if one is specified, is also invoked on the
** auxiliary data pointer after the FTS5 query has finished.
**
** If an error (e.g. an OOM condition) occurs within this function,
** the auxiliary data is set to NULL and an error code returned. If the
** xDelete parameter was not NULL, it is invoked on the auxiliary data
** pointer before returning.
**
**
** xGetAuxdata(pFts5, bClear)
**
** Returns the current auxiliary data pointer for the fts5 extension
** function. See the xSetAuxdata() method for details.
**
** If the bClear argument is non-zero, then the auxiliary data is cleared
** (set to NULL) before this function returns. In this case the xDelete,
** if any, is not invoked.
**
**
** xRowCount(pFts5, pnRow)
**
** This function is used to retrieve the total number of rows in the table.
** In other words, the same value that would be returned by:
**
** SELECT count(*) FROM ftstable;
**
** xPhraseFirst()
** This function is used, along with type Fts5PhraseIter and the xPhraseNext
** method, to iterate through all instances of a single query phrase within
** the current row. This is the same information as is accessible via the
** xInstCount/xInst APIs. While the xInstCount/xInst APIs are more convenient
** to use, this API may be faster under some circumstances. To iterate
** through instances of phrase iPhrase, use the following code:
**
** Fts5PhraseIter iter;
** int iCol, iOff;
** for(pApi->xPhraseFirst(pFts, iPhrase, &iter, &iCol, &iOff);
** iCol>=0;
** pApi->xPhraseNext(pFts, &iter, &iCol, &iOff)
** ){
** // An instance of phrase iPhrase at offset iOff of column iCol
** }
**
** The Fts5PhraseIter structure is defined above. Applications should not
** modify this structure directly - it should only be used as shown above
** with the xPhraseFirst() and xPhraseNext() API methods (and by
** xPhraseFirstColumn() and xPhraseNextColumn() as illustrated below).
**
** This API can be quite slow if used with an FTS5 table created with the
** "detail=none" or "detail=column" option. If the FTS5 table is created
** with either "detail=none" or "detail=column" and "content=" option
** (i.e. if it is a contentless table), then this API always iterates
** through an empty set (all calls to xPhraseFirst() set iCol to -1).
**
** In all cases, matches are visited in (column ASC, offset ASC) order.
** i.e. all those in column 0, sorted by offset, followed by those in
** column 1, etc.
**
** xPhraseNext()
** See xPhraseFirst above.
**
** xPhraseFirstColumn()
** This function and xPhraseNextColumn() are similar to the xPhraseFirst()
** and xPhraseNext() APIs described above. The difference is that instead
** of iterating through all instances of a phrase in the current row, these
** APIs are used to iterate through the set of columns in the current row
** that contain one or more instances of a specified phrase. For example:
**
** Fts5PhraseIter iter;
** int iCol;
** for(pApi->xPhraseFirstColumn(pFts, iPhrase, &iter, &iCol);
** iCol>=0;
** pApi->xPhraseNextColumn(pFts, &iter, &iCol)
** ){
** // Column iCol contains at least one instance of phrase iPhrase
** }
**
** This API can be quite slow if used with an FTS5 table created with the
** "detail=none" option. If the FTS5 table is created with either
** "detail=none" "content=" option (i.e. if it is a contentless table),
** then this API always iterates through an empty set (all calls to
** xPhraseFirstColumn() set iCol to -1).
**
** The information accessed using this API and its companion
** xPhraseFirstColumn() may also be obtained using xPhraseFirst/xPhraseNext
** (or xInst/xInstCount). The chief advantage of this API is that it is
** significantly more efficient than those alternatives when used with
** "detail=column" tables.
**
** xPhraseNextColumn()
** See xPhraseFirstColumn above.
**
** xQueryToken(pFts5, iPhrase, iToken, ppToken, pnToken)
** This is used to access token iToken of phrase iPhrase of the current
** query. Before returning, output parameter *ppToken is set to point
** to a buffer containing the requested token, and *pnToken to the
** size of this buffer in bytes.
**
** If iPhrase or iToken are less than zero, or if iPhrase is greater than
** or equal to the number of phrases in the query as reported by
** xPhraseCount(), or if iToken is equal to or greater than the number of
** tokens in the phrase, SQLITE_RANGE is returned and *ppToken and *pnToken
 are both zeroed.
**
** The output text is not a copy of the query text that specified the
** token. It is the output of the tokenizer module. For tokendata=1
** tables, this includes any embedded 0x00 and trailing data.
**
** xInstToken(pFts5, iIdx, iToken, ppToken, pnToken)
** This is used to access token iToken of phrase hit iIdx within the
** current row. If iIdx is less than zero or greater than or equal to the
** value returned by xInstCount(), SQLITE_RANGE is returned. Otherwise,
** output variable (*ppToken) is set to point to a buffer containing the
** matching document token, and (*pnToken) to the size of that buffer in
** bytes. This API is not available if the specified token matches a
** prefix query term. In that case both output variables are always set
** to 0.
**
** The output text is not a copy of the document text that was tokenized.
** It is the output of the tokenizer module. For tokendata=1 tables, this
** includes any embedded 0x00 and trailing data.
**
** This API can be quite slow if used with an FTS5 table created with the
** "detail=none" or "detail=column" option.
**
** xColumnLocale(pFts5, iIdx, pzLocale, pnLocale)
** If parameter iCol is less than zero, or greater than or equal to the
** number of columns in the table, SQLITE_RANGE is returned.
**
** Otherwise, this function attempts to retrieve the locale associated
** with column iCol of the current row. Usually, there is no associated
** locale, and output parameters (*pzLocale) and (*pnLocale) are set
** to NULL and 0, respectively. However, if the fts5_locale() function
** was used to associate a locale with the value when it was inserted
** into the fts5 table, then (*pzLocale) is set to point to a nul-terminated
** buffer containing the name of the locale in utf-8 encoding. (*pnLocale)
** is set to the size in bytes of the buffer, not including the
** nul-terminator.
**
** If successful, SQLITE_OK is returned. Or, if an error occurs, an
** SQLite error code is returned. The final value of the output parameters
** is undefined in this case.
**
** xTokenize_v2:
** Tokenize text using the tokenizer belonging to the FTS5 table. This
** API is the same as the xTokenize() API, except that it allows a tokenizer
** locale to be specified.
*/
struct Fts5ExtensionApi {
 int iVersion; /* Currently always set to 4 */

 void *(*xUserData)(Fts5Context*);

 int (*xColumnCount)(Fts5Context*);
 int (*xRowCount)(Fts5Context*, sqlite3_int64 *pnRow);
 int (*xColumnTotalSize)(Fts5Context*, int iCol, sqlite3_int64 *pnToken);

 int (*xTokenize)(Fts5Context*,
 const char *pText, int nText, /* Text to tokenize */
 void *pCtx, /* Context passed to xToken() */
 int (*xToken)(void*, int, const char*, int, int, int) /* Callback */
 );

 int (*xPhraseCount)(Fts5Context*);
 int (*xPhraseSize)(Fts5Context*, int iPhrase);

 int (*xInstCount)(Fts5Context*, int *pnInst);
 int (*xInst)(Fts5Context*, int iIdx, int *piPhrase, int *piCol, int *piOff);

 sqlite3_int64 (*xRowid)(Fts5Context*);
 int (*xColumnText)(Fts5Context*, int iCol, const char **pz, int *pn);
 int (*xColumnSize)(Fts5Context*, int iCol, int *pnToken);

 int (*xQueryPhrase)(Fts5Context*, int iPhrase, void *pUserData,
 int(*)(const Fts5ExtensionApi*,Fts5Context*,void*)
 );
 int (*xSetAuxdata)(Fts5Context*, void *pAux, void(*xDelete)(void*));
 void *(*xGetAuxdata)(Fts5Context*, int bClear);

 int (*xPhraseFirst)(Fts5Context*, int iPhrase, Fts5PhraseIter*, int*, int*);
 void (*xPhraseNext)(Fts5Context*, Fts5PhraseIter*, int *piCol, int *piOff);

 int (*xPhraseFirstColumn)(Fts5Context*, int iPhrase, Fts5PhraseIter*, int*);
 void (*xPhraseNextColumn)(Fts5Context*, Fts5PhraseIter*, int *piCol);

 /* Below this point are iVersion>=3 only */
 int (*xQueryToken)(Fts5Context*,
 int iPhrase, int iToken,
 const char **ppToken, int *pnToken
 );
 int (*xInstToken)(Fts5Context*, int iIdx, int iToken, const char**, int*);

 /* Below this point are iVersion>=4 only */
 int (*xColumnLocale)(Fts5Context*, int iCol, const char **pz, int *pn);
 int (*xTokenize_v2)(Fts5Context*,
 const char *pText, int nText, /* Text to tokenize */
 const char *pLocale, int nLocale, /* Locale to pass to tokenizer */
 void *pCtx, /* Context passed to xToken() */
 int (*xToken)(void*, int, const char*, int, int, int) /* Callback */
 );
};

/*
** CUSTOM AUXILIARY FUNCTIONS
*************************************************************************/

/*************************************************************************
** CUSTOM TOKENIZERS
**
** Applications may also register custom tokenizer types. A tokenizer
** is registered by providing fts5 with a populated instance of the
** following structure. All structure methods must be defined, setting
** any member of the fts5_tokenizer struct to NULL leads to undefined
** behaviour. The structure methods are expected to function as follows:
**
** xCreate:
** This function is used to allocate and initialize a tokenizer instance.
** A tokenizer instance is required to actually tokenize text.
**
** The first argument passed to this function is a copy of the (void*)
** pointer provided by the application when the fts5_tokenizer_v2 object
** was registered with FTS5 (the third argument to xCreateTokenizer()).
** The second and third arguments are an array of nul-terminated strings
** containing the tokenizer arguments, if any, specified following the
** tokenizer name as part of the CREATE VIRTUAL TABLE statement used
** to create the FTS5 table.
**
** The final argument is an output variable. If successful, (*ppOut)
** should be set to point to the new tokenizer handle and SQLITE_OK
** returned. If an error occurs, some value other than SQLITE_OK should
** be returned. In this case, fts5 assumes that the final value of *ppOut
** is undefined.
**
** xDelete:
** This function is invoked to delete a tokenizer handle previously
** allocated using xCreate(). Fts5 guarantees that this function will
** be invoked exactly once for each successful call to xCreate().
**
** xTokenize:
** This function is expected to tokenize the nText byte string indicated
** by argument pText. pText may or may not be nul-terminated. The first
** argument passed to this function is a pointer to an Fts5Tokenizer object
** returned by an earlier call to xCreate().
**
** The third argument indicates the reason that FTS5 is requesting
** tokenization of the supplied text. This is always one of the following
** four values:
**
** <ul><li> FTS5_TOKENIZE_DOCUMENT - A document is being inserted into
** or removed from the FTS table. The tokenizer is being invoked to
** determine the set of tokens to add to (or delete from) the
** FTS index.
**
** <li> FTS5_TOKENIZE_QUERY - A MATCH query is being executed
** against the FTS index. The tokenizer is being called to tokenize
** a bareword or quoted string specified as part of the query.
**
** <li> (FTS5_TOKENIZE_QUERY | FTS5_TOKENIZE_PREFIX) - Same as
** FTS5_TOKENIZE_QUERY, except that the bareword or quoted string is
** followed by a "*" character, indicating that the last token
** returned by the tokenizer will be treated as a token prefix.
**
** <li> FTS5_TOKENIZE_AUX - The tokenizer is being invoked to
** satisfy an fts5_api.xTokenize() request made by an auxiliary
** function. Or an fts5_api.xColumnSize() request made by the same
** on a columnsize=0 database.
** </ul>
**
** The sixth and seventh arguments passed to xTokenize() - pLocale and
** nLocale - are a pointer to a buffer containing the locale to use for
** tokenization (e.g. "en_US") and its size in bytes, respectively. The
** pLocale buffer is not nul-terminated. pLocale may be passed NULL (in
** which case nLocale is always 0) to indicate that the tokenizer should
** use its default locale.
**
** For each token in the input string, the supplied callback xToken() must
** be invoked. The first argument to it should be a copy of the pointer
** passed as the second argument to xTokenize(). The third and fourth
** arguments are a pointer to a buffer containing the token text, and the
** size of the token in bytes. The 4th and 5th arguments are the byte offsets
** of the first byte of and first byte immediately following the text from
** which the token is derived within the input.
**
** The second argument passed to the xToken() callback ("tflags") should
** normally be set to 0. The exception is if the tokenizer supports
** synonyms. In this case see the discussion below for details.
**
** FTS5 assumes the xToken() callback is invoked for each token in the
** order that they occur within the input text.
**
** If an xToken() callback returns any value other than SQLITE_OK, then
** the tokenization should be abandoned and the xTokenize() method should
** immediately return a copy of the xToken() return value. Or, if the
** input buffer is exhausted, xTokenize() should return SQLITE_OK. Finally,
** if an error occurs with the xTokenize() implementation itself, it
** may abandon the tokenization and return any error code other than
** SQLITE_OK or SQLITE_DONE.
**
** If the tokenizer is registered using an fts5_tokenizer_v2 object,
** then the xTokenize() method has two additional arguments - pLocale
** and nLocale. These specify the locale that the tokenizer should use
** for the current request. If pLocale and nLocale are both 0, then the
** tokenizer should use its default locale. Otherwise, pLocale points to
** an nLocale byte buffer containing the name of the locale to use as utf-8
** text. pLocale is not nul-terminated.
**
** FTS5_TOKENIZER
**
** There is also an fts5_tokenizer object. This is an older, deprecated,
** version of fts5_tokenizer_v2. It is similar except that:
**
** <ul>
** <li> There is no "iVersion" field, and
** <li> The xTokenize() method does not take a locale argument.
** </ul>
**
** Legacy fts5_tokenizer tokenizers must be registered using the
** legacy xCreateTokenizer() function, instead of xCreateTokenizer_v2().
**
** Tokenizer implementations registered using either API may be retrieved
** using both xFindTokenizer() and xFindTokenizer_v2().
**
** SYNONYM SUPPORT
**
** Custom tokenizers may also support synonyms. Consider a case in which a
** user wishes to query for a phrase such as "first place". Using the
** built-in tokenizers, the FTS5 query 'first + place' will match instances
** of "first place" within the document set, but not alternative forms
** such as "1st place". In some applications, it would be better to match
** all instances of "first place" or "1st place" regardless of which form
** the user specified in the MATCH query text.
**
** There are several ways to approach this in FTS5:
**
** <ol><li> By mapping all synonyms to a single token. In this case, using
** the above example, this means that the tokenizer returns the
** same token for inputs "first" and "1st". Say that token is in
** fact "first", so that when the user inserts the document "I won
** 1st place" entries are added to the index for tokens "i", "won",
** "first" and "place". If the user then queries for '1st + place',
** the tokenizer substitutes "first" for "1st" and the query works
** as expected.
**
** <li> By querying the index for all synonyms of each query term
** separately. In this case, when tokenizing query text, the
** tokenizer may provide multiple synonyms for a single term
** within the document. FTS5 then queries the index for each
** synonym individually. For example, faced with the query:
**
** <codeblock>
** ... MATCH 'first place'</codeblock>
**
** the tokenizer offers both "1st" and "first" as synonyms for the
** first token in the MATCH query and FTS5 effectively runs a query
** similar to:
**
** <codeblock>
** ... MATCH '(first OR 1st) place'</codeblock>
**
** except that, for the purposes of auxiliary functions, the query
** still appears to contain just two phrases - "(first OR 1st)"
** being treated as a single phrase.
**
** <li> By adding multiple synonyms for a single term to the FTS index.
** Using this method, when tokenizing document text, the tokenizer
** provides multiple synonyms for each token. So that when a
** document such as "I won first place" is tokenized, entries are
** added to the FTS index for "i", "won", "first", "1st" and
** "place".
**
** This way, even if the tokenizer does not provide synonyms
** when tokenizing query text (it should not - to do so would be
** inefficient), it doesn't matter if the user queries for
** 'first + place' or '1st + place', as there are entries in the
** FTS index corresponding to both forms of the first token.
** </ol>
**
** Whether it is parsing document or query text, any call to xToken that
** specifies a tflags argument with the FTS5_TOKEN_COLOCATED bit
** is considered to supply a synonym for the previous token. For example,
** when parsing the document "I won first place", a tokenizer that supports
** synonyms would call xToken() 5 times, as follows:
**
** <codeblock>
** xToken(pCtx, 0, "i", 1, 0, 1);
** xToken(pCtx, 0, "won", 3, 2, 5);
** xToken(pCtx, 0, "first", 5, 6, 11);
** xToken(pCtx, FTS5_TOKEN_COLOCATED, "1st", 3, 6, 11);
** xToken(pCtx, 0, "place", 5, 12, 17);
**</codeblock>
**
** It is an error to specify the FTS5_TOKEN_COLOCATED flag the first time
** xToken() is called. Multiple synonyms may be specified for a single token
** by making multiple calls to xToken(FTS5_TOKEN_COLOCATED) in sequence.
** There is no limit to the number of synonyms that may be provided for a
** single token.
**
** In many cases, method (1) above is the best approach. It does not add
** extra data to the FTS index or require FTS5 to query for multiple terms,
** so it is efficient in terms of disk space and query speed. However, it
** does not support prefix queries very well. If, as suggested above, the
** token "first" is substituted for "1st" by the tokenizer, then the query:
**
** <codeblock>
** ... MATCH '1s*'</codeblock>
**
** will not match documents that contain the token "1st" (as the tokenizer
** will probably not map "1s" to any prefix of "first").
**
** For full prefix support, method (3) may be preferred. In this case,
** because the index contains entries for both "first" and "1st", prefix
** queries such as 'fi*' or '1s*' will match correctly. However, because
** extra entries are added to the FTS index, this method uses more space
** within the database.
**
** Method (2) offers a midpoint between (1) and (3). Using this method,
** a query such as '1s*' will match documents that contain the literal
** token "1st", but not "first" (assuming the tokenizer is not able to
** provide synonyms for prefixes). However, a non-prefix query like '1st'
** will match against "1st" and "first". This method does not require
** extra disk space, as no extra entries are added to the FTS index.
** On the other hand, it may require more CPU cycles to run MATCH queries,
** as separate queries of the FTS index are required for each synonym.
**
** When using methods (2) or (3), it is important that the tokenizer only
** provide synonyms when tokenizing document text (method (3)) or query
** text (method (2)), not both. Doing so will not cause any errors, but is
** inefficient.
*/
typedef struct Fts5Tokenizer Fts5Tokenizer;
typedef struct fts5_tokenizer_v2 fts5_tokenizer_v2;
struct fts5_tokenizer_v2 {
 int iVersion; /* Currently always 2 */

 int (*xCreate)(void*, const char **azArg, int nArg, Fts5Tokenizer **ppOut);
 void (*xDelete)(Fts5Tokenizer*);
 int (*xTokenize)(Fts5Tokenizer*,
 void *pCtx,
 int flags, /* Mask of FTS5_TOKENIZE_* flags */
 const char *pText, int nText,
 const char *pLocale, int nLocale,
 int (*xToken)(
 void *pCtx, /* Copy of 2nd argument to xTokenize() */
 int tflags, /* Mask of FTS5_TOKEN_* flags */
 const char *pToken, /* Pointer to buffer containing token */
 int nToken, /* Size of token in bytes */
 int iStart, /* Byte offset of token within input text */
 int iEnd /* Byte offset of end of token within input text */
 )
 );
};

/*
** New code should use the fts5_tokenizer_v2 type to define tokenizer
** implementations. The following type is included for legacy applications
** that still use it.
*/
typedef struct fts5_tokenizer fts5_tokenizer;
struct fts5_tokenizer {
 int (*xCreate)(void*, const char **azArg, int nArg, Fts5Tokenizer **ppOut);
 void (*xDelete)(Fts5Tokenizer*);
 int (*xTokenize)(Fts5Tokenizer*,
 void *pCtx,
 int flags, /* Mask of FTS5_TOKENIZE_* flags */
 const char *pText, int nText,
 int (*xToken)(
 void *pCtx, /* Copy of 2nd argument to xTokenize() */
 int tflags, /* Mask of FTS5_TOKEN_* flags */
 const char *pToken, /* Pointer to buffer containing token */
 int nToken, /* Size of token in bytes */
 int iStart, /* Byte offset of token within input text */
 int iEnd /* Byte offset of end of token within input text */
 )
 );
};

/* Flags that may be passed as the third argument to xTokenize() */
#define FTS5_TOKENIZE_QUERY 0x0001
#define FTS5_TOKENIZE_PREFIX 0x0002
#define FTS5_TOKENIZE_DOCUMENT 0x0004
#define FTS5_TOKENIZE_AUX 0x0008

/* Flags that may be passed by the tokenizer implementation back to FTS5
** as the third argument to the supplied xToken callback. */
#define FTS5_TOKEN_COLOCATED 0x0001 /* Same position as prev. token */

/*
** END OF CUSTOM TOKENIZERS
*************************************************************************/

/*************************************************************************
** FTS5 EXTENSION REGISTRATION API
*/
typedef struct fts5_api fts5_api;
struct fts5_api {
 int iVersion; /* Currently always set to 3 */

 /* Create a new tokenizer */
 int (*xCreateTokenizer)(
 fts5_api *pApi,
 const char *zName,
 void *pUserData,
 fts5_tokenizer *pTokenizer,
 void (*xDestroy)(void*)
 );

 /* Find an existing tokenizer */
 int (*xFindTokenizer)(
 fts5_api *pApi,
 const char *zName,
 void **ppUserData,
 fts5_tokenizer *pTokenizer
 );

 /* Create a new auxiliary function */
 int (*xCreateFunction)(
 fts5_api *pApi,
 const char *zName,
 void *pUserData,
 fts5_extension_function xFunction,
 void (*xDestroy)(void*)
 );

 /* APIs below this point are only available if iVersion>=3 */

 /* Create a new tokenizer */
 int (*xCreateTokenizer_v2)(
 fts5_api *pApi,
 const char *zName,
 void *pUserData,
 fts5_tokenizer_v2 *pTokenizer,
 void (*xDestroy)(void*)
 );

 /* Find an existing tokenizer */
 int (*xFindTokenizer_v2)(
 fts5_api *pApi,
 const char *zName,
 void **ppUserData,
 fts5_tokenizer_v2 **ppTokenizer
 );
};

/*
** END OF REGISTRATION API
*************************************************************************/

#ifdef __cplusplus
} /* end of the 'extern "C"' block */
#endif

#endif /* _FTS5_H */

#line 1 "fts5Int.h"
/*
** 2014 May 31
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
*/
#ifndef _FTS5INT_H
#define _FTS5INT_H

/* #include "fts5.h" */
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1

#include <string.h>
#include <assert.h>

#ifndef SQLITE_AMALGAMATION

typedef unsigned char u8;
typedef unsigned int u32;
typedef unsigned short u16;
typedef short i16;
typedef sqlite3_int64 i64;
typedef sqlite3_uint64 u64;

#ifndef ArraySize
# define ArraySize(x) ((int)(sizeof(x) / sizeof(x[0])))
#endif

#define testcase(x)

#if defined(SQLITE_COVERAGE_TEST) || defined(SQLITE_MUTATION_TEST)
# define SQLITE_OMIT_AUXILIARY_SAFETY_CHECKS 1
#endif
#if defined(SQLITE_OMIT_AUXILIARY_SAFETY_CHECKS)
# define ALWAYS(X) (1)
# define NEVER(X) (0)
#elif !defined(NDEBUG)
# define ALWAYS(X) ((X)?1:(assert(0),0))
# define NEVER(X) ((X)?(assert(0),1):0)
#else
# define ALWAYS(X) (X)
# define NEVER(X) (X)
#endif

#define MIN(x,y) (((x) < (y)) ? (x) : (y))
#define MAX(x,y) (((x) > (y)) ? (x) : (y))

/*
** Constants for the largest and smallest possible 64-bit signed integers.
*/
# define LARGEST_INT64 (0xffffffff|(((i64)0x7fffffff)<<32))
# define SMALLEST_INT64 (((i64)-1) - LARGEST_INT64)

/* The uptr type is an unsigned integer large enough to hold a pointer
*/
#if defined(HAVE_STDINT_H)
 typedef uintptr_t uptr;
#elif SQLITE_PTRSIZE==4
 typedef u32 uptr;
#else
 typedef u64 uptr;
#endif

#ifdef SQLITE_4_BYTE_ALIGNED_MALLOC
# define EIGHT_BYTE_ALIGNMENT(X) ((((uptr)(X) - (uptr)0)&3)==0)
#else
# define EIGHT_BYTE_ALIGNMENT(X) ((((uptr)(X) - (uptr)0)&7)==0)
#endif

#endif

/* Truncate very long tokens to this many bytes. Hard limit is
** (65536-1-1-4-9)==65521 bytes. The limiting factor is the 16-bit offset
** field that occurs at the start of each leaf page (see fts5_index.c). */
#define FTS5_MAX_TOKEN_SIZE 32768

/*
** Maximum number of prefix indexes on single FTS5 table. This must be
** less than 32. If it is set to anything large than that, an #error
** directive in fts5_index.c will cause the build to fail.
*/
#define FTS5_MAX_PREFIX_INDEXES 31

/*
** Maximum segments permitted in a single index
*/
#define FTS5_MAX_SEGMENT 2000

#define FTS5_DEFAULT_NEARDIST 10
#define FTS5_DEFAULT_RANK "bm25"

/* Name of rank and rowid columns */
#define FTS5_RANK_NAME "rank"
#define FTS5_ROWID_NAME "rowid"

#ifdef SQLITE_DEBUG
# define FTS5_CORRUPT sqlite3Fts5Corrupt()
static int sqlite3Fts5Corrupt(void);
#else
# define FTS5_CORRUPT SQLITE_CORRUPT_VTAB
#endif

/*
** The assert_nc() macro is similar to the assert() macro, except that it
** is used for assert() conditions that are true only if it can be
** guranteed that the database is not corrupt.
*/
#ifdef SQLITE_DEBUG
extern int sqlite3_fts5_may_be_corrupt;
# define assert_nc(x) assert(sqlite3_fts5_may_be_corrupt || (x))
#else
# define assert_nc(x) assert(x)
#endif

/*
** A version of memcmp() that does not cause asan errors if one of the pointer
** parameters is NULL and the number of bytes to compare is zero.
*/
#define fts5Memcmp(s1, s2, n) ((n)<=0 ? 0 : memcmp((s1), (s2), (n)))

/* Mark a function parameter as unused, to suppress nuisance compiler
** warnings. */
#ifndef UNUSED_PARAM
# define UNUSED_PARAM(X) (void)(X)
#endif

#ifndef UNUSED_PARAM2
# define UNUSED_PARAM2(X, Y) (void)(X), (void)(Y)
#endif

typedef struct Fts5Global Fts5Global;
typedef struct Fts5Colset Fts5Colset;

/* If a NEAR() clump or phrase may only match a specific set of columns,
** then an object of the following type is used to record the set of columns.
** Each entry in the aiCol[] array is a column that may be matched.
**
** This object is used by fts5_expr.c and fts5_index.c.
*/
struct Fts5Colset {
 int nCol;
 int aiCol[1];
};

/**************************************************************************
** Interface to code in fts5_config.c. fts5_config.c contains contains code
** to parse the arguments passed to the CREATE VIRTUAL TABLE statement.
*/

typedef struct Fts5Config Fts5Config;
typedef struct Fts5TokenizerConfig Fts5TokenizerConfig;

struct Fts5TokenizerConfig {
 Fts5Tokenizer *pTok;
 fts5_tokenizer_v2 *pApi2;
 fts5_tokenizer *pApi1;
 const char **azArg;
 int nArg;
 int ePattern; /* FTS_PATTERN_XXX constant */
 const char *pLocale; /* Current locale to use */
 int nLocale; /* Size of pLocale in bytes */
};

/*
** An instance of the following structure encodes all information that can
** be gleaned from the CREATE VIRTUAL TABLE statement.
**
** And all information loaded from the %_config table.
**
** nAutomerge:
** The minimum number of segments that an auto-merge operation should
** attempt to merge together. A value of 1 sets the object to use the
** compile time default. Zero disables auto-merge altogether.
**
** bContentlessDelete:
** True if the contentless_delete option was present in the CREATE
** VIRTUAL TABLE statement.
**
** zContent:
**
** zContentRowid:
** The value of the content_rowid= option, if one was specified. Or
** the string "rowid" otherwise. This text is not quoted - if it is
** used as part of an SQL statement it needs to be quoted appropriately.
**
** zContentExprlist:
**
** pzErrmsg:
** This exists in order to allow the fts5_index.c module to return a
** decent error message if it encounters a file-format version it does
** not understand.
**
** bColumnsize:
** True if the %_docsize table is created.
**
** bPrefixIndex:
** This is only used for debugging. If set to false, any prefix indexes
** are ignored. This value is configured using:
**
** INSERT INTO tbl(tbl, rank) VALUES('prefix-index', $bPrefixIndex);
**
** bLocale:
** Set to true if locale=1 was specified when the table was created.
*/
struct Fts5Config {
 sqlite3 *db; /* Database handle */
 Fts5Global *pGlobal; /* Global fts5 object for handle db */
 char *zDb; /* Database holding FTS index (e.g. "main") */
 char *zName; /* Name of FTS index */
 int nCol; /* Number of columns */
 char **azCol; /* Column names */
 u8 *abUnindexed; /* True for unindexed columns */
 int nPrefix; /* Number of prefix indexes */
 int *aPrefix; /* Sizes in bytes of nPrefix prefix indexes */
 int eContent; /* An FTS5_CONTENT value */
 int bContentlessDelete; /* "contentless_delete=" option (dflt==0) */
 int bContentlessUnindexed; /* "contentless_unindexed=" option (dflt=0) */
 char *zContent; /* content table */
 char *zContentRowid; /* "content_rowid=" option value */
 int bColumnsize; /* "columnsize=" option value (dflt==1) */
 int bTokendata; /* "tokendata=" option value (dflt==0) */
 int bLocale; /* "locale=" option value (dflt==0) */
 int eDetail; /* FTS5_DETAIL_XXX value */
 char *zContentExprlist;
 Fts5TokenizerConfig t;
 int bLock; /* True when table is preparing statement */


 /* Values loaded from the %_config table */
 int iVersion; /* fts5 file format 'version' */
 int iCookie; /* Incremented when %_config is modified */
 int pgsz; /* Approximate page size used in %_data */
 int nAutomerge; /* 'automerge' setting */
 int nCrisisMerge; /* Maximum allowed segments per level */
 int nUsermerge; /* 'usermerge' setting */
 int nHashSize; /* Bytes of memory for in-memory hash */
 char *zRank; /* Name of rank function */
 char *zRankArgs; /* Arguments to rank function */
 int bSecureDelete; /* 'secure-delete' */
 int nDeleteMerge; /* 'deletemerge' */

 /* If non-NULL, points to sqlite3_vtab.base.zErrmsg. Often NULL. */
 char **pzErrmsg;

#ifdef SQLITE_DEBUG
 int bPrefixIndex; /* True to use prefix-indexes */
#endif
};

/* Current expected value of %_config table 'version' field. And
** the expected version if the 'secure-delete' option has ever been
** set on the table. */
#define FTS5_CURRENT_VERSION 4
#define FTS5_CURRENT_VERSION_SECUREDELETE 5

#define FTS5_CONTENT_NORMAL 0
#define FTS5_CONTENT_NONE 1
#define FTS5_CONTENT_EXTERNAL 2
#define FTS5_CONTENT_UNINDEXED 3

#define FTS5_DETAIL_FULL 0
#define FTS5_DETAIL_NONE 1
#define FTS5_DETAIL_COLUMNS 2

#define FTS5_PATTERN_NONE 0
#define FTS5_PATTERN_LIKE 65 /* matches SQLITE_INDEX_CONSTRAINT_LIKE */
#define FTS5_PATTERN_GLOB 66 /* matches SQLITE_INDEX_CONSTRAINT_GLOB */

static int sqlite3Fts5ConfigParse(
 Fts5Global*, sqlite3*, int, const char **, Fts5Config**, char**
);
static void sqlite3Fts5ConfigFree(Fts5Config*);

static int sqlite3Fts5ConfigDeclareVtab(Fts5Config *pConfig);

static int sqlite3Fts5Tokenize(
 Fts5Config *pConfig, /* FTS5 Configuration object */
 int flags, /* FTS5_TOKENIZE_* flags */
 const char *pText, int nText, /* Text to tokenize */
 void *pCtx, /* Context passed to xToken() */
 int (*xToken)(void*, int, const char*, int, int, int) /* Callback */
);

static void sqlite3Fts5Dequote(char *z);

/* Load the contents of the %_config table */
static int sqlite3Fts5ConfigLoad(Fts5Config*, int);

/* Set the value of a single config attribute */
static int sqlite3Fts5ConfigSetValue(Fts5Config*, const char*, sqlite3_value*, int*);

static int sqlite3Fts5ConfigParseRank(const char*, char**, char**);

static void sqlite3Fts5ConfigErrmsg(Fts5Config *pConfig, const char *zFmt, ...);

/*
** End of interface to code in fts5_config.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_buffer.c.
*/

/*
** Buffer object for the incremental building of string data.
*/
typedef struct Fts5Buffer Fts5Buffer;
struct Fts5Buffer {
 u8 *p;
 int n;
 int nSpace;
};

static int sqlite3Fts5BufferSize(int*, Fts5Buffer*, u32);
static void sqlite3Fts5BufferAppendVarint(int*, Fts5Buffer*, i64);
static void sqlite3Fts5BufferAppendBlob(int*, Fts5Buffer*, u32, const u8*);
static void sqlite3Fts5BufferAppendString(int *, Fts5Buffer*, const char*);
static void sqlite3Fts5BufferFree(Fts5Buffer*);
static void sqlite3Fts5BufferZero(Fts5Buffer*);
static void sqlite3Fts5BufferSet(int*, Fts5Buffer*, int, const u8*);
static void sqlite3Fts5BufferAppendPrintf(int *, Fts5Buffer*, char *zFmt, ...);

static char *sqlite3Fts5Mprintf(int *pRc, const char *zFmt, ...);

#define fts5BufferZero(x) sqlite3Fts5BufferZero(x)
#define fts5BufferAppendVarint(a,b,c) sqlite3Fts5BufferAppendVarint(a,b,(i64)c)
#define fts5BufferFree(a) sqlite3Fts5BufferFree(a)
#define fts5BufferAppendBlob(a,b,c,d) sqlite3Fts5BufferAppendBlob(a,b,c,d)
#define fts5BufferSet(a,b,c,d) sqlite3Fts5BufferSet(a,b,c,d)

#define fts5BufferGrow(pRc,pBuf,nn) ( \
 (u32)((pBuf)->n) + (u32)(nn) <= (u32)((pBuf)->nSpace) ? 0 : \
 sqlite3Fts5BufferSize((pRc),(pBuf),(nn)+(pBuf)->n) \
)

/* Write and decode big-endian 32-bit integer values */
static void sqlite3Fts5Put32(u8*, int);
static int sqlite3Fts5Get32(const u8*);

#define FTS5_POS2COLUMN(iPos) (int)((iPos >> 32) & 0x7FFFFFFF)
#define FTS5_POS2OFFSET(iPos) (int)(iPos & 0x7FFFFFFF)

typedef struct Fts5PoslistReader Fts5PoslistReader;
struct Fts5PoslistReader {
 /* Variables used only by sqlite3Fts5PoslistIterXXX() functions. */
 const u8 *a; /* Position list to iterate through */
 int n; /* Size of buffer at a[] in bytes */
 int i; /* Current offset in a[] */

 u8 bFlag; /* For client use (any custom purpose) */

 /* Output variables */
 u8 bEof; /* Set to true at EOF */
 i64 iPos; /* (iCol<<32) + iPos */
};
static int sqlite3Fts5PoslistReaderInit(
 const u8 *a, int n, /* Poslist buffer to iterate through */
 Fts5PoslistReader *pIter /* Iterator object to initialize */
);
static int sqlite3Fts5PoslistReaderNext(Fts5PoslistReader*);

typedef struct Fts5PoslistWriter Fts5PoslistWriter;
struct Fts5PoslistWriter {
 i64 iPrev;
};
static int sqlite3Fts5PoslistWriterAppend(Fts5Buffer*, Fts5PoslistWriter*, i64);
static void sqlite3Fts5PoslistSafeAppend(Fts5Buffer*, i64*, i64);

static int sqlite3Fts5PoslistNext64(
 const u8 *a, int n, /* Buffer containing poslist */
 int *pi, /* IN/OUT: Offset within a[] */
 i64 *piOff /* IN/OUT: Current offset */
);

/* Malloc utility */
static void *sqlite3Fts5MallocZero(int *pRc, sqlite3_int64 nByte);
static char *sqlite3Fts5Strndup(int *pRc, const char *pIn, int nIn);

/* Character set tests (like isspace(), isalpha() etc.) */
static int sqlite3Fts5IsBareword(char t);

/* Bucket of terms object used by the integrity-check in offsets=0 mode. */
typedef struct Fts5Termset Fts5Termset;
static int sqlite3Fts5TermsetNew(Fts5Termset**);
static int sqlite3Fts5TermsetAdd(Fts5Termset*, int, const char*, int, int *pbPresent);
static void sqlite3Fts5TermsetFree(Fts5Termset*);

/*
** End of interface to code in fts5_buffer.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_index.c. fts5_index.c contains contains code
** to access the data stored in the %_data table.
*/

typedef struct Fts5Index Fts5Index;
typedef struct Fts5IndexIter Fts5IndexIter;

struct Fts5IndexIter {
 i64 iRowid;
 const u8 *pData;
 int nData;
 u8 bEof;
};

#define sqlite3Fts5IterEof(x) ((x)->bEof)

/*
** Values used as part of the flags argument passed to IndexQuery().
*/
#define FTS5INDEX_QUERY_PREFIX 0x0001 /* Prefix query */
#define FTS5INDEX_QUERY_DESC 0x0002 /* Docs in descending rowid order */
#define FTS5INDEX_QUERY_TEST_NOIDX 0x0004 /* Do not use prefix index */
#define FTS5INDEX_QUERY_SCAN 0x0008 /* Scan query (fts5vocab) */

/* The following are used internally by the fts5_index.c module. They are
** defined here only to make it easier to avoid clashes with the flags
** above. */
#define FTS5INDEX_QUERY_SKIPEMPTY 0x0010
#define FTS5INDEX_QUERY_NOOUTPUT 0x0020
#define FTS5INDEX_QUERY_SKIPHASH 0x0040
#define FTS5INDEX_QUERY_NOTOKENDATA 0x0080
#define FTS5INDEX_QUERY_SCANONETERM 0x0100

/*
** Create/destroy an Fts5Index object.
*/
static int sqlite3Fts5IndexOpen(Fts5Config *pConfig, int bCreate, Fts5Index**, char**);
static int sqlite3Fts5IndexClose(Fts5Index *p);

/*
** Return a simple checksum value based on the arguments.
*/
static u64 sqlite3Fts5IndexEntryCksum(
 i64 iRowid,
 int iCol,
 int iPos,
 int iIdx,
 const char *pTerm,
 int nTerm
);

/*
** Argument p points to a buffer containing utf-8 text that is n bytes in
** size. Return the number of bytes in the nChar character prefix of the
** buffer, or 0 if there are less than nChar characters in total.
*/
static int sqlite3Fts5IndexCharlenToBytelen(
 const char *p,
 int nByte,
 int nChar
);

/*
** Open a new iterator to iterate though all rowids that match the
** specified token or token prefix.
*/
static int sqlite3Fts5IndexQuery(
 Fts5Index *p, /* FTS index to query */
 const char *pToken, int nToken, /* Token (or prefix) to query for */
 int flags, /* Mask of FTS5INDEX_QUERY_X flags */
 Fts5Colset *pColset, /* Match these columns only */
 Fts5IndexIter **ppIter /* OUT: New iterator object */
);

/*
** The various operations on open token or token prefix iterators opened
** using sqlite3Fts5IndexQuery().
*/
static int sqlite3Fts5IterNext(Fts5IndexIter*);
static int sqlite3Fts5IterNextFrom(Fts5IndexIter*, i64 iMatch);

/*
** Close an iterator opened by sqlite3Fts5IndexQuery().
*/
static void sqlite3Fts5IterClose(Fts5IndexIter*);

/*
** Close the reader blob handle, if it is open.
*/
static void sqlite3Fts5IndexCloseReader(Fts5Index*);

/*
** This interface is used by the fts5vocab module.
*/
static const char *sqlite3Fts5IterTerm(Fts5IndexIter*, int*);
static int sqlite3Fts5IterNextScan(Fts5IndexIter*);
static void *sqlite3Fts5StructureRef(Fts5Index*);
static void sqlite3Fts5StructureRelease(void*);
static int sqlite3Fts5StructureTest(Fts5Index*, void*);

/*
** Used by xInstToken():
*/
static int sqlite3Fts5IterToken(Fts5IndexIter*, i64, int, int, const char**, int*);

/*
** Insert or remove data to or from the index. Each time a document is
** added to or removed from the index, this function is called one or more
** times.
**
** For an insert, it must be called once for each token in the new document.
** If the operation is a delete, it must be called (at least) once for each
** unique token in the document with an iCol value less than zero. The iPos
** argument is ignored for a delete.
*/
static int sqlite3Fts5IndexWrite(
 Fts5Index *p, /* Index to write to */
 int iCol, /* Column token appears in (-ve -> delete) */
 int iPos, /* Position of token within column */
 const char *pToken, int nToken /* Token to add or remove to or from index */
);

/*
** Indicate that subsequent calls to sqlite3Fts5IndexWrite() pertain to
** document iDocid.
*/
static int sqlite3Fts5IndexBeginWrite(
 Fts5Index *p, /* Index to write to */
 int bDelete, /* True if current operation is a delete */
 i64 iDocid /* Docid to add or remove data from */
);

/*
** Flush any data stored in the in-memory hash tables to the database.
** Also close any open blob handles.
*/
static int sqlite3Fts5IndexSync(Fts5Index *p);

/*
** Discard any data stored in the in-memory hash tables. Do not write it
** to the database. Additionally, assume that the contents of the %_data
** table may have changed on disk. So any in-memory caches of %_data
** records must be invalidated.
*/
static int sqlite3Fts5IndexRollback(Fts5Index *p);

/*
** Get or set the "averages" values.
*/
static int sqlite3Fts5IndexGetAverages(Fts5Index *p, i64 *pnRow, i64 *anSize);
static int sqlite3Fts5IndexSetAverages(Fts5Index *p, const u8*, int);

/*
** Functions called by the storage module as part of integrity-check.
*/
static int sqlite3Fts5IndexIntegrityCheck(Fts5Index*, u64 cksum, int bUseCksum);

/*
** Called during virtual module initialization to register UDF
** fts5_decode() with SQLite
*/
static int sqlite3Fts5IndexInit(sqlite3*);

static int sqlite3Fts5IndexSetCookie(Fts5Index*, int);

/*
** Return the total number of entries read from the %_data table by
** this connection since it was created.
*/
static int sqlite3Fts5IndexReads(Fts5Index *p);

static int sqlite3Fts5IndexReinit(Fts5Index *p);
static int sqlite3Fts5IndexOptimize(Fts5Index *p);
static int sqlite3Fts5IndexMerge(Fts5Index *p, int nMerge);
static int sqlite3Fts5IndexReset(Fts5Index *p);

static int sqlite3Fts5IndexLoadConfig(Fts5Index *p);

static int sqlite3Fts5IndexGetOrigin(Fts5Index *p, i64 *piOrigin);
static int sqlite3Fts5IndexContentlessDelete(Fts5Index *p, i64 iOrigin, i64 iRowid);

static void sqlite3Fts5IndexIterClearTokendata(Fts5IndexIter*);

/* Used to populate hash tables for xInstToken in detail=none/column mode. */
static int sqlite3Fts5IndexIterWriteTokendata(
 Fts5IndexIter*, const char*, int, i64 iRowid, int iCol, int iOff
);

/*
** End of interface to code in fts5_index.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_varint.c.
*/
static int sqlite3Fts5GetVarint32(const unsigned char *p, u32 *v);
static int sqlite3Fts5GetVarintLen(u32 iVal);
static u8 sqlite3Fts5GetVarint(const unsigned char*, u64*);
static int sqlite3Fts5PutVarint(unsigned char *p, u64 v);

#define fts5GetVarint32(a,b) sqlite3Fts5GetVarint32(a,(u32*)&(b))
#define fts5GetVarint sqlite3Fts5GetVarint

#define fts5FastGetVarint32(a, iOff, nVal) { \
 nVal = (a)[iOff++]; \
 if( nVal & 0x80 ){ \
 iOff--; \
 iOff += fts5GetVarint32(&(a)[iOff], nVal); \
 } \
}

/*
** End of interface to code in fts5_varint.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_main.c.
*/

/*
** Virtual-table object.
*/
typedef struct Fts5Table Fts5Table;
struct Fts5Table {
 sqlite3_vtab base; /* Base class used by SQLite core */
 Fts5Config *pConfig; /* Virtual table configuration */
 Fts5Index *pIndex; /* Full-text index */
};

static int sqlite3Fts5LoadTokenizer(Fts5Config *pConfig);

static Fts5Table *sqlite3Fts5TableFromCsrid(Fts5Global*, i64);

static int sqlite3Fts5FlushToDisk(Fts5Table*);

static void sqlite3Fts5ClearLocale(Fts5Config *pConfig);
static void sqlite3Fts5SetLocale(Fts5Config *pConfig, const char *pLoc, int nLoc);

static int sqlite3Fts5IsLocaleValue(Fts5Config *pConfig, sqlite3_value *pVal);
static int sqlite3Fts5DecodeLocaleValue(sqlite3_value *pVal,
 const char **ppText, int *pnText, const char **ppLoc, int *pnLoc
);

/*
** End of interface to code in fts5.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_hash.c.
*/
typedef struct Fts5Hash Fts5Hash;

/*
** Create a hash table, free a hash table.
*/
static int sqlite3Fts5HashNew(Fts5Config*, Fts5Hash**, int *pnSize);
static void sqlite3Fts5HashFree(Fts5Hash*);

static int sqlite3Fts5HashWrite(
 Fts5Hash*,
 i64 iRowid, /* Rowid for this entry */
 int iCol, /* Column token appears in (-ve -> delete) */
 int iPos, /* Position of token within column */
 char bByte,
 const char *pToken, int nToken /* Token to add or remove to or from index */
);

/*
** Empty (but do not delete) a hash table.
*/
static void sqlite3Fts5HashClear(Fts5Hash*);

/*
** Return true if the hash is empty, false otherwise.
*/
static int sqlite3Fts5HashIsEmpty(Fts5Hash*);

static int sqlite3Fts5HashQuery(
 Fts5Hash*, /* Hash table to query */
 int nPre,
 const char *pTerm, int nTerm, /* Query term */
 void **ppObj, /* OUT: Pointer to doclist for pTerm */
 int *pnDoclist /* OUT: Size of doclist in bytes */
);

static int sqlite3Fts5HashScanInit(
 Fts5Hash*, /* Hash table to query */
 const char *pTerm, int nTerm /* Query prefix */
);
static void sqlite3Fts5HashScanNext(Fts5Hash*);
static int sqlite3Fts5HashScanEof(Fts5Hash*);
static void sqlite3Fts5HashScanEntry(Fts5Hash *,
 const char **pzTerm, /* OUT: term (nul-terminated) */
 int *pnTerm, /* OUT: Size of term in bytes */
 const u8 **ppDoclist, /* OUT: pointer to doclist */
 int *pnDoclist /* OUT: size of doclist in bytes */
);

/*
** End of interface to code in fts5_hash.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_storage.c. fts5_storage.c contains contains
** code to access the data stored in the %_content and %_docsize tables.
*/

#define FTS5_STMT_SCAN_ASC 0 /* SELECT rowid, * FROM ... ORDER BY 1 ASC */
#define FTS5_STMT_SCAN_DESC 1 /* SELECT rowid, * FROM ... ORDER BY 1 DESC */
#define FTS5_STMT_LOOKUP 2 /* SELECT rowid, * FROM ... WHERE rowid=? */

typedef struct Fts5Storage Fts5Storage;

static int sqlite3Fts5StorageOpen(Fts5Config*, Fts5Index*, int, Fts5Storage**, char**);
static int sqlite3Fts5StorageClose(Fts5Storage *p);
static int sqlite3Fts5StorageRename(Fts5Storage*, const char *zName);

static int sqlite3Fts5DropAll(Fts5Config*);
static int sqlite3Fts5CreateTable(Fts5Config*, const char*, const char*, int, char **);

static int sqlite3Fts5StorageDelete(Fts5Storage *p, i64, sqlite3_value**, int);
static int sqlite3Fts5StorageContentInsert(Fts5Storage *p, int, sqlite3_value**, i64*);
static int sqlite3Fts5StorageIndexInsert(Fts5Storage *p, sqlite3_value**, i64);

static int sqlite3Fts5StorageIntegrity(Fts5Storage *p, int iArg);

static int sqlite3Fts5StorageStmt(Fts5Storage *p, int eStmt, sqlite3_stmt**, char**);
static void sqlite3Fts5StorageStmtRelease(Fts5Storage *p, int eStmt, sqlite3_stmt*);

static int sqlite3Fts5StorageDocsize(Fts5Storage *p, i64 iRowid, int *aCol);
static int sqlite3Fts5StorageSize(Fts5Storage *p, int iCol, i64 *pnAvg);
static int sqlite3Fts5StorageRowCount(Fts5Storage *p, i64 *pnRow);

static int sqlite3Fts5StorageSync(Fts5Storage *p);
static int sqlite3Fts5StorageRollback(Fts5Storage *p);

static int sqlite3Fts5StorageConfigValue(
 Fts5Storage *p, const char*, sqlite3_value*, int
);

static int sqlite3Fts5StorageDeleteAll(Fts5Storage *p);
static int sqlite3Fts5StorageRebuild(Fts5Storage *p);
static int sqlite3Fts5StorageOptimize(Fts5Storage *p);
static int sqlite3Fts5StorageMerge(Fts5Storage *p, int nMerge);
static int sqlite3Fts5StorageReset(Fts5Storage *p);

static void sqlite3Fts5StorageReleaseDeleteRow(Fts5Storage*);
static int sqlite3Fts5StorageFindDeleteRow(Fts5Storage *p, i64 iDel);

/*
** End of interface to code in fts5_storage.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_expr.c.
*/
typedef struct Fts5Expr Fts5Expr;
typedef struct Fts5ExprNode Fts5ExprNode;
typedef struct Fts5Parse Fts5Parse;
typedef struct Fts5Token Fts5Token;
typedef struct Fts5ExprPhrase Fts5ExprPhrase;
typedef struct Fts5ExprNearset Fts5ExprNearset;

struct Fts5Token {
 const char *p; /* Token text (not NULL terminated) */
 int n; /* Size of buffer p in bytes */
};

/* Parse a MATCH expression. */
static int sqlite3Fts5ExprNew(
 Fts5Config *pConfig,
 int bPhraseToAnd,
 int iCol, /* Column on LHS of MATCH operator */
 const char *zExpr,
 Fts5Expr **ppNew,
 char **pzErr
);
static int sqlite3Fts5ExprPattern(
 Fts5Config *pConfig,
 int bGlob,
 int iCol,
 const char *zText,
 Fts5Expr **pp
);

/*
** for(rc = sqlite3Fts5ExprFirst(pExpr, pIdx, bDesc);
** rc==SQLITE_OK && 0==sqlite3Fts5ExprEof(pExpr);
** rc = sqlite3Fts5ExprNext(pExpr)
** ){
** // The document with rowid iRowid matches the expression!
** i64 iRowid = sqlite3Fts5ExprRowid(pExpr);
** }
*/
static int sqlite3Fts5ExprFirst(Fts5Expr*, Fts5Index *pIdx, i64 iMin, int bDesc);
static int sqlite3Fts5ExprNext(Fts5Expr*, i64 iMax);
static int sqlite3Fts5ExprEof(Fts5Expr*);
static i64 sqlite3Fts5ExprRowid(Fts5Expr*);

static void sqlite3Fts5ExprFree(Fts5Expr*);
static int sqlite3Fts5ExprAnd(Fts5Expr **pp1, Fts5Expr *p2);

/* Called during startup to register a UDF with SQLite */
static int sqlite3Fts5ExprInit(Fts5Global*, sqlite3*);

static int sqlite3Fts5ExprPhraseCount(Fts5Expr*);
static int sqlite3Fts5ExprPhraseSize(Fts5Expr*, int iPhrase);
static int sqlite3Fts5ExprPoslist(Fts5Expr*, int, const u8 **);

typedef struct Fts5PoslistPopulator Fts5PoslistPopulator;
static Fts5PoslistPopulator *sqlite3Fts5ExprClearPoslists(Fts5Expr*, int);
static int sqlite3Fts5ExprPopulatePoslists(
 Fts5Config*, Fts5Expr*, Fts5PoslistPopulator*, int, const char*, int
);
static void sqlite3Fts5ExprCheckPoslists(Fts5Expr*, i64);

static int sqlite3Fts5ExprClonePhrase(Fts5Expr*, int, Fts5Expr**);

static int sqlite3Fts5ExprPhraseCollist(Fts5Expr *, int, const u8 **, int *);

static int sqlite3Fts5ExprQueryToken(Fts5Expr*, int, int, const char**, int*);
static int sqlite3Fts5ExprInstToken(Fts5Expr*, i64, int, int, int, int, const char**, int*);
static void sqlite3Fts5ExprClearTokens(Fts5Expr*);

/*******************************************
** The fts5_expr.c API above this point is used by the other hand-written
** C code in this module. The interfaces below this point are called by
** the parser code in fts5parse.y. */

static void sqlite3Fts5ParseError(Fts5Parse *pParse, const char *zFmt, ...);

static Fts5ExprNode *sqlite3Fts5ParseNode(
 Fts5Parse *pParse,
 int eType,
 Fts5ExprNode *pLeft,
 Fts5ExprNode *pRight,
 Fts5ExprNearset *pNear
);

static Fts5ExprNode *sqlite3Fts5ParseImplicitAnd(
 Fts5Parse *pParse,
 Fts5ExprNode *pLeft,
 Fts5ExprNode *pRight
);

static Fts5ExprPhrase *sqlite3Fts5ParseTerm(
 Fts5Parse *pParse,
 Fts5ExprPhrase *pPhrase,
 Fts5Token *pToken,
 int bPrefix
);

static void sqlite3Fts5ParseSetCaret(Fts5ExprPhrase*);

static Fts5ExprNearset *sqlite3Fts5ParseNearset(
 Fts5Parse*,
 Fts5ExprNearset*,
 Fts5ExprPhrase*
);

static Fts5Colset *sqlite3Fts5ParseColset(
 Fts5Parse*,
 Fts5Colset*,
 Fts5Token *
);

static void sqlite3Fts5ParsePhraseFree(Fts5ExprPhrase*);
static void sqlite3Fts5ParseNearsetFree(Fts5ExprNearset*);
static void sqlite3Fts5ParseNodeFree(Fts5ExprNode*);

static void sqlite3Fts5ParseSetDistance(Fts5Parse*, Fts5ExprNearset*, Fts5Token*);
static void sqlite3Fts5ParseSetColset(Fts5Parse*, Fts5ExprNode*, Fts5Colset*);
static Fts5Colset *sqlite3Fts5ParseColsetInvert(Fts5Parse*, Fts5Colset*);
static void sqlite3Fts5ParseFinished(Fts5Parse *pParse, Fts5ExprNode *p);
static void sqlite3Fts5ParseNear(Fts5Parse *pParse, Fts5Token*);

/*
** End of interface to code in fts5_expr.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_aux.c.
*/

static int sqlite3Fts5AuxInit(fts5_api*);
/*
** End of interface to code in fts5_aux.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_tokenizer.c.
*/

static int sqlite3Fts5TokenizerInit(fts5_api*);
static int sqlite3Fts5TokenizerPattern(
 int (*xCreate)(void*, const char**, int, Fts5Tokenizer**),
 Fts5Tokenizer *pTok
);
static int sqlite3Fts5TokenizerPreload(Fts5TokenizerConfig*);
/*
** End of interface to code in fts5_tokenizer.c.
**************************************************************************/

/**************************************************************************
** Interface to code in fts5_vocab.c.
*/

static int sqlite3Fts5VocabInit(Fts5Global*, sqlite3*);

/*
** End of interface to code in fts5_vocab.c.
**************************************************************************/

/**************************************************************************
** Interface to automatically generated code in fts5_unicode2.c.
*/
static int sqlite3Fts5UnicodeIsdiacritic(int c);
static int sqlite3Fts5UnicodeFold(int c, int bRemoveDiacritic);

static int sqlite3Fts5UnicodeCatParse(const char*, u8*);
static int sqlite3Fts5UnicodeCategory(u32 iCode);
static void sqlite3Fts5UnicodeAscii(u8*, u8*);
/*
** End of interface to code in fts5_unicode2.c.
**************************************************************************/

#endif

#line 1 "fts5parse.h"
#define FTS5_OR 1
#define FTS5_AND 2
#define FTS5_NOT 3
#define FTS5_TERM 4
#define FTS5_COLON 5
#define FTS5_MINUS 6
#define FTS5_LCP 7
#define FTS5_RCP 8
#define FTS5_STRING 9
#define FTS5_LP 10
#define FTS5_RP 11
#define FTS5_CARET 12
#define FTS5_COMMA 13
#define FTS5_PLUS 14
#define FTS5_STAR 15

#line 1 "fts5parse.c"
/* This file is automatically generated by Lemon from input grammar
** source file "fts5parse.y".
*/
/*
** 2000-05-29
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** Driver template for the LEMON parser generator.
**
** The "lemon" program processes an LALR(1) input grammar file, then uses
** this template to construct a parser. The "lemon" program inserts text
** at each "%%" line. Also, any "P-a-r-s-e" identifer prefix (without the
** interstitial "-" characters) contained in this template is changed into
** the value of the %name directive from the grammar. Otherwise, the content
** of this template is copied straight through into the generate parser
** source file.
**
** The following is the concatenation of all %include directives from the
** input grammar file:
*/
/************ Begin %include sections from the grammar ************************/
#line 47 "fts5parse.y"

/* #include "fts5Int.h" */
/* #include "fts5parse.h" */

/*
** Disable all error recovery processing in the parser push-down
** automaton.
*/
#define fts5YYNOERRORRECOVERY 1

/*
** Make fts5yytestcase() the same as testcase()
*/
#define fts5yytestcase(X) testcase(X)

/*
** Indicate that sqlite3ParserFree() will never be called with a null
** pointer.
*/
#define fts5YYPARSEFREENOTNULL 1

/*
** Alternative datatype for the argument to the malloc() routine passed
** into sqlite3ParserAlloc(). The default is size_t.
*/
#define fts5YYMALLOCARGTYPE u64

#line 58 "fts5parse.sql"
/**************** End of %include directives **********************************/
/* These constants specify the various numeric values for terminal symbols.
***************** Begin token definitions *************************************/
#ifndef FTS5_OR
#define FTS5_OR 1
#define FTS5_AND 2
#define FTS5_NOT 3
#define FTS5_TERM 4
#define FTS5_COLON 5
#define FTS5_MINUS 6
#define FTS5_LCP 7
#define FTS5_RCP 8
#define FTS5_STRING 9
#define FTS5_LP 10
#define FTS5_RP 11
#define FTS5_CARET 12
#define FTS5_COMMA 13
#define FTS5_PLUS 14
#define FTS5_STAR 15
#endif
/**************** End token definitions ***************************************/

/* The next sections is a series of control #defines.
** various aspects of the generated parser.
** fts5YYCODETYPE is the data type used to store the integer codes
** that represent terminal and non-terminal symbols.
** "unsigned char" is used if there are fewer than
** 256 symbols. Larger types otherwise.
** fts5YYNOCODE is a number of type fts5YYCODETYPE that is not used for
** any terminal or nonterminal symbol.
** fts5YYFALLBACK If defined, this indicates that one or more tokens
** (also known as: "terminal symbols") have fall-back
** values which should be used if the original symbol
** would not parse. This permits keywords to sometimes
** be used as identifiers, for example.
** fts5YYACTIONTYPE is the data type used for "action codes" - numbers
** that indicate what to do in response to the next
** token.
** sqlite3Fts5ParserFTS5TOKENTYPE is the data type used for minor type for terminal
** symbols. Background: A "minor type" is a semantic
** value associated with a terminal or non-terminal
** symbols. For example, for an "ID" terminal symbol,
** the minor type might be the name of the identifier.
** Each non-terminal can have a different minor type.
** Terminal symbols all have the same minor type, though.
** This macros defines the minor type for terminal
** symbols.
** fts5YYMINORTYPE is the data type used for all minor types.
** This is typically a union of many types, one of
** which is sqlite3Fts5ParserFTS5TOKENTYPE. The entry in the union
** for terminal symbols is called "fts5yy0".
** fts5YYSTACKDEPTH is the maximum depth of the parser's stack. If
** zero the stack is dynamically sized using realloc()
** sqlite3Fts5ParserARG_SDECL A static variable declaration for the %extra_argument
** sqlite3Fts5ParserARG_PDECL A parameter declaration for the %extra_argument
** sqlite3Fts5ParserARG_PARAM Code to pass %extra_argument as a subroutine parameter
** sqlite3Fts5ParserARG_STORE Code to store %extra_argument into fts5yypParser
** sqlite3Fts5ParserARG_FETCH Code to extract %extra_argument from fts5yypParser
** sqlite3Fts5ParserCTX_* As sqlite3Fts5ParserARG_ except for %extra_context
** fts5YYREALLOC Name of the realloc() function to use
** fts5YYFREE Name of the free() function to use
** fts5YYDYNSTACK True if stack space should be extended on heap
** fts5YYERRORSYMBOL is the code number of the error symbol. If not
** defined, then do no error processing.
** fts5YYNSTATE the combined number of states.
** fts5YYNRULE the number of rules in the grammar
** fts5YYNFTS5TOKEN Number of terminal symbols
** fts5YY_MAX_SHIFT Maximum value for shift actions
** fts5YY_MIN_SHIFTREDUCE Minimum value for shift-reduce actions
** fts5YY_MAX_SHIFTREDUCE Maximum value for shift-reduce actions
** fts5YY_ERROR_ACTION The fts5yy_action[] code for syntax error
** fts5YY_ACCEPT_ACTION The fts5yy_action[] code for accept
** fts5YY_NO_ACTION The fts5yy_action[] code for no-op
** fts5YY_MIN_REDUCE Minimum value for reduce actions
** fts5YY_MAX_REDUCE Maximum value for reduce actions
** fts5YY_MIN_DSTRCTR Minimum symbol value that has a destructor
** fts5YY_MAX_DSTRCTR Maximum symbol value that has a destructor
*/
#ifndef INTERFACE
# define INTERFACE 1
#endif
/************* Begin control #defines *****************************************/
#define fts5YYCODETYPE unsigned char
#define fts5YYNOCODE 27
#define fts5YYACTIONTYPE unsigned char
#define sqlite3Fts5ParserFTS5TOKENTYPE Fts5Token
typedef union {
 int fts5yyinit;
 sqlite3Fts5ParserFTS5TOKENTYPE fts5yy0;
 int fts5yy4;
 Fts5Colset* fts5yy11;
 Fts5ExprNode* fts5yy24;
 Fts5ExprNearset* fts5yy46;
 Fts5ExprPhrase* fts5yy53;
} fts5YYMINORTYPE;
#ifndef fts5YYSTACKDEPTH
#define fts5YYSTACKDEPTH 100
#endif
#define sqlite3Fts5ParserARG_SDECL Fts5Parse *pParse;
#define sqlite3Fts5ParserARG_PDECL ,Fts5Parse *pParse
#define sqlite3Fts5ParserARG_PARAM ,pParse
#define sqlite3Fts5ParserARG_FETCH Fts5Parse *pParse=fts5yypParser->pParse;
#define sqlite3Fts5ParserARG_STORE fts5yypParser->pParse=pParse;
#define fts5YYREALLOC realloc
#define fts5YYFREE free
#define fts5YYDYNSTACK 0
#define sqlite3Fts5ParserCTX_SDECL
#define sqlite3Fts5ParserCTX_PDECL
#define sqlite3Fts5ParserCTX_PARAM
#define sqlite3Fts5ParserCTX_FETCH
#define sqlite3Fts5ParserCTX_STORE
#define fts5YYNSTATE 35
#define fts5YYNRULE 28
#define fts5YYNRULE_WITH_ACTION 28
#define fts5YYNFTS5TOKEN 16
#define fts5YY_MAX_SHIFT 34
#define fts5YY_MIN_SHIFTREDUCE 52
#define fts5YY_MAX_SHIFTREDUCE 79
#define fts5YY_ERROR_ACTION 80
#define fts5YY_ACCEPT_ACTION 81
#define fts5YY_NO_ACTION 82
#define fts5YY_MIN_REDUCE 83
#define fts5YY_MAX_REDUCE 110
#define fts5YY_MIN_DSTRCTR 16
#define fts5YY_MAX_DSTRCTR 24
/************* End control #defines *******************************************/
#define fts5YY_NLOOKAHEAD ((int)(sizeof(fts5yy_lookahead)/sizeof(fts5yy_lookahead[0])))

/* Define the fts5yytestcase() macro to be a no-op if is not already defined
** otherwise.
**
** Applications can choose to define fts5yytestcase() in the %include section
** to a macro that can assist in verifying code coverage. For production
** code the fts5yytestcase() macro should be turned off. But it is useful
** for testing.
*/
#ifndef fts5yytestcase
# define fts5yytestcase(X)
#endif

/* Macro to determine if stack space has the ability to grow using
** heap memory.
*/
#if fts5YYSTACKDEPTH<=0 || fts5YYDYNSTACK
# define fts5YYGROWABLESTACK 1
#else
# define fts5YYGROWABLESTACK 0
#endif

/* Guarantee a minimum number of initial stack slots.
*/
#if fts5YYSTACKDEPTH<=0
# undef fts5YYSTACKDEPTH
# define fts5YYSTACKDEPTH 2 /* Need a minimum stack size */
#endif

/* Next are the tables used to determine what action to take based on the
** current state and lookahead token. These tables are used to implement
** functions that take a state number and lookahead value and return an
** action integer.
**
** Suppose the action integer is N. Then the action is determined as
** follows
**
** 0 <= N <= fts5YY_MAX_SHIFT Shift N. That is, push the lookahead
** token onto the stack and goto state N.
**
** N between fts5YY_MIN_SHIFTREDUCE Shift to an arbitrary state then
** and fts5YY_MAX_SHIFTREDUCE reduce by rule N-fts5YY_MIN_SHIFTREDUCE.
**
** N == fts5YY_ERROR_ACTION A syntax error has occurred.
**
** N == fts5YY_ACCEPT_ACTION The parser accepts its input.
**
** N == fts5YY_NO_ACTION No such action. Denotes unused
** slots in the fts5yy_action[] table.
**
** N between fts5YY_MIN_REDUCE Reduce by rule N-fts5YY_MIN_REDUCE
** and fts5YY_MAX_REDUCE
**
** The action table is constructed as a single large table named fts5yy_action[].
** Given state S and lookahead X, the action is computed as either:
**
** (A) N = fts5yy_action[ fts5yy_shift_ofst[S] + X ]
** (B) N = fts5yy_default[S]
**
** The (A) formula is preferred. The B formula is used instead if
** fts5yy_lookahead[fts5yy_shift_ofst[S]+X] is not equal to X.
**
** The formulas above are for computing the action when the lookahead is
** a terminal symbol. If the lookahead is a non-terminal (as occurs after
** a reduce action) then the fts5yy_reduce_ofst[] array is used in place of
** the fts5yy_shift_ofst[] array.
**
** The following are the tables generated in this section:
**
** fts5yy_action[] A single table containing all actions.
** fts5yy_lookahead[] A table containing the lookahead for each entry in
** fts5yy_action. Used to detect hash collisions.
** fts5yy_shift_ofst[] For each state, the offset into fts5yy_action for
** shifting terminals.
** fts5yy_reduce_ofst[] For each state, the offset into fts5yy_action for
** shifting non-terminals after a reduce.
** fts5yy_default[] Default action for each state.
**
*********** Begin parsing tables **********************************************/
#define fts5YY_ACTTAB_COUNT (105)
static const fts5YYACTIONTYPE fts5yy_action[] = {
/* 0 */ 81, 20, 96, 6, 28, 99, 98, 26, 26, 18,
/* 10 */ 96, 6, 28, 17, 98, 56, 26, 19, 96, 6,
/* 20 */ 28, 14, 98, 14, 26, 31, 92, 96, 6, 28,
/* 30 */ 108, 98, 25, 26, 21, 96, 6, 28, 78, 98,
/* 40 */ 58, 26, 29, 96, 6, 28, 107, 98, 22, 26,
/* 50 */ 24, 16, 12, 11, 1, 13, 13, 24, 16, 23,
/* 60 */ 11, 33, 34, 13, 97, 8, 27, 32, 98, 7,
/* 70 */ 26, 3, 4, 5, 3, 4, 5, 3, 83, 4,
/* 80 */ 5, 3, 63, 5, 3, 62, 12, 2, 86, 13,
/* 90 */ 9, 30, 10, 10, 54, 57, 75, 78, 78, 53,
/* 100 */ 57, 15, 82, 82, 71,
};
static const fts5YYCODETYPE fts5yy_lookahead[] = {
/* 0 */ 16, 17, 18, 19, 20, 22, 22, 24, 24, 17,
/* 10 */ 18, 19, 20, 7, 22, 9, 24, 17, 18, 19,
/* 20 */ 20, 9, 22, 9, 24, 13, 17, 18, 19, 20,
/* 30 */ 26, 22, 24, 24, 17, 18, 19, 20, 15, 22,
/* 40 */ 9, 24, 17, 18, 19, 20, 26, 22, 21, 24,
/* 50 */ 6, 7, 9, 9, 10, 12, 12, 6, 7, 21,
/* 60 */ 9, 24, 25, 12, 18, 5, 20, 14, 22, 5,
/* 70 */ 24, 3, 1, 2, 3, 1, 2, 3, 0, 1,
/* 80 */ 2, 3, 11, 2, 3, 11, 9, 10, 5, 12,
/* 90 */ 23, 24, 10, 10, 8, 9, 9, 15, 15, 8,
/* 100 */ 9, 9, 27, 27, 11, 27, 27, 27, 27, 27,
/* 110 */ 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
/* 120 */ 27,
};
#define fts5YY_SHIFT_COUNT (34)
#define fts5YY_SHIFT_MIN (0)
#define fts5YY_SHIFT_MAX (93)
static const unsigned char fts5yy_shift_ofst[] = {
/* 0 */ 44, 44, 44, 44, 44, 44, 51, 77, 43, 12,
/* 10 */ 14, 83, 82, 14, 23, 23, 31, 31, 71, 74,
/* 20 */ 78, 81, 86, 91, 6, 53, 53, 60, 64, 68,
/* 30 */ 53, 87, 92, 53, 93,
};
#define fts5YY_REDUCE_COUNT (17)
#define fts5YY_REDUCE_MIN (-17)
#define fts5YY_REDUCE_MAX (67)
static const signed char fts5yy_reduce_ofst[] = {
/* 0 */ -16, -8, 0, 9, 17, 25, 46, -17, -17, 37,
/* 10 */ 67, 4, 4, 8, 4, 20, 27, 38,
};
static const fts5YYACTIONTYPE fts5yy_default[] = {
/* 0 */ 80, 80, 80, 80, 80, 80, 95, 80, 80, 105,
/* 10 */ 80, 110, 110, 80, 110, 110, 80, 80, 80, 80,
/* 20 */ 80, 91, 80, 80, 80, 101, 100, 80, 80, 90,
/* 30 */ 103, 80, 80, 104, 80,
};
/********** End of lemon-generated parsing tables *****************************/

/* The next table maps tokens (terminal symbols) into fallback tokens.
** If a construct like the following:
**
** %fallback ID X Y Z.
**
** appears in the grammar, then ID becomes a fallback token for X, Y,
** and Z. Whenever one of the tokens X, Y, or Z is input to the parser
** but it does not parse, the type of the token is changed to ID and
** the parse is retried before an error is thrown.
**
** This feature can be used, for example, to cause some keywords in a language
** to revert to identifiers if they keyword does not apply in the context where
** it appears.
*/
#ifdef fts5YYFALLBACK
static const fts5YYCODETYPE fts5yyFallback[] = {
};
#endif /* fts5YYFALLBACK */

/* The following structure represents a single element of the
** parser's stack. Information stored includes:
**
** + The state number for the parser at this level of the stack.
**
** + The value of the token stored at this level of the stack.
** (In other words, the "major" token.)
**
** + The semantic value stored at this level of the stack. This is
** the information used by the action routines in the grammar.
** It is sometimes called the "minor" token.
**
** After the "shift" half of a SHIFTREDUCE action, the stateno field
** actually contains the reduce action for the second half of the
** SHIFTREDUCE.
*/
struct fts5yyStackEntry {
 fts5YYACTIONTYPE stateno; /* The state-number, or reduce action in SHIFTREDUCE */
 fts5YYCODETYPE major; /* The major token value. This is the code
 ** number for the token at this stack level */
 fts5YYMINORTYPE minor; /* The user-supplied minor token value. This
 ** is the value of the token */
};
typedef struct fts5yyStackEntry fts5yyStackEntry;

/* The state of the parser is completely contained in an instance of
** the following structure */
struct fts5yyParser {
 fts5yyStackEntry *fts5yytos; /* Pointer to top element of the stack */
#ifdef fts5YYTRACKMAXSTACKDEPTH
 int fts5yyhwm; /* High-water mark of the stack */
#endif
#ifndef fts5YYNOERRORRECOVERY
 int fts5yyerrcnt; /* Shifts left before out of the error */
#endif
 sqlite3Fts5ParserARG_SDECL /* A place to hold %extra_argument */
 sqlite3Fts5ParserCTX_SDECL /* A place to hold %extra_context */
 fts5yyStackEntry *fts5yystackEnd; /* Last entry in the stack */
 fts5yyStackEntry *fts5yystack; /* The parser stack */
 fts5yyStackEntry fts5yystk0[fts5YYSTACKDEPTH]; /* Initial stack space */
};
typedef struct fts5yyParser fts5yyParser;

#include <assert.h>
#ifndef NDEBUG
#include <stdio.h>
static FILE *fts5yyTraceFILE = 0;
static char *fts5yyTracePrompt = 0;
#endif /* NDEBUG */

#ifndef NDEBUG
/*
** Turn parser tracing on by giving a stream to which to write the trace
** and a prompt to preface each trace message. Tracing is turned off
** by making either argument NULL
**
** Inputs:
** <ul>
** <li> A FILE* to which trace output should be written.
** If NULL, then tracing is turned off.
** <li> A prefix string written at the beginning of every
** line of trace output. If NULL, then tracing is
** turned off.
** </ul>
**
** Outputs:
** None.
*/
static void sqlite3Fts5ParserTrace(FILE *TraceFILE, char *zTracePrompt){
 fts5yyTraceFILE = TraceFILE;
 fts5yyTracePrompt = zTracePrompt;
 if( fts5yyTraceFILE==0 ) fts5yyTracePrompt = 0;
 else if( fts5yyTracePrompt==0 ) fts5yyTraceFILE = 0;
}
#endif /* NDEBUG */

#if defined(fts5YYCOVERAGE) || !defined(NDEBUG)
/* For tracing shifts, the names of all terminals and nonterminals
** are required. The following table supplies these names */
static const char *const fts5yyTokenName[] = {
 /* 0 */ "$",
 /* 1 */ "OR",
 /* 2 */ "AND",
 /* 3 */ "NOT",
 /* 4 */ "TERM",
 /* 5 */ "COLON",
 /* 6 */ "MINUS",
 /* 7 */ "LCP",
 /* 8 */ "RCP",
 /* 9 */ "STRING",
 /* 10 */ "LP",
 /* 11 */ "RP",
 /* 12 */ "CARET",
 /* 13 */ "COMMA",
 /* 14 */ "PLUS",
 /* 15 */ "STAR",
 /* 16 */ "input",
 /* 17 */ "expr",
 /* 18 */ "cnearset",
 /* 19 */ "exprlist",
 /* 20 */ "colset",
 /* 21 */ "colsetlist",
 /* 22 */ "nearset",
 /* 23 */ "nearphrases",
 /* 24 */ "phrase",
 /* 25 */ "neardist_opt",
 /* 26 */ "star_opt",
};
#endif /* defined(fts5YYCOVERAGE) || !defined(NDEBUG) */

#ifndef NDEBUG
/* For tracing reduce actions, the names of all rules are required.
*/
static const char *const fts5yyRuleName[] = {
/* 0 */ "input ::= expr",
/* 1 */ "colset ::= MINUS LCP colsetlist RCP",
/* 2 */ "colset ::= LCP colsetlist RCP",
/* 3 */ "colset ::= STRING",
/* 4 */ "colset ::= MINUS STRING",
/* 5 */ "colsetlist ::= colsetlist STRING",
/* 6 */ "colsetlist ::= STRING",
/* 7 */ "expr ::= expr AND expr",
/* 8 */ "expr ::= expr OR expr",
/* 9 */ "expr ::= expr NOT expr",
/* 10 */ "expr ::= colset COLON LP expr RP",
/* 11 */ "expr ::= LP expr RP",
/* 12 */ "expr ::= exprlist",
/* 13 */ "exprlist ::= cnearset",
/* 14 */ "exprlist ::= exprlist cnearset",
/* 15 */ "cnearset ::= nearset",
/* 16 */ "cnearset ::= colset COLON nearset",
/* 17 */ "nearset ::= phrase",
/* 18 */ "nearset ::= CARET phrase",
/* 19 */ "nearset ::= STRING LP nearphrases neardist_opt RP",
/* 20 */ "nearphrases ::= phrase",
/* 21 */ "nearphrases ::= nearphrases phrase",
/* 22 */ "neardist_opt ::=",
/* 23 */ "neardist_opt ::= COMMA STRING",
/* 24 */ "phrase ::= phrase PLUS STRING star_opt",
/* 25 */ "phrase ::= STRING star_opt",
/* 26 */ "star_opt ::= STAR",
/* 27 */ "star_opt ::=",
};
#endif /* NDEBUG */

#if fts5YYGROWABLESTACK
/*
** Try to increase the size of the parser stack. Return the number
** of errors. Return 0 on success.
*/
static int fts5yyGrowStack(fts5yyParser *p){
 int oldSize = 1 + (int)(p->fts5yystackEnd - p->fts5yystack);
 int newSize;
 int idx;
 fts5yyStackEntry *pNew;

 newSize = oldSize*2 + 100;
 idx = (int)(p->fts5yytos - p->fts5yystack);
 if( p->fts5yystack==p->fts5yystk0 ){
 pNew = fts5YYREALLOC(0, newSize*sizeof(pNew[0]));
 if( pNew==0 ) return 1;
 memcpy(pNew, p->fts5yystack, oldSize*sizeof(pNew[0]));
 }else{
 pNew = fts5YYREALLOC(p->fts5yystack, newSize*sizeof(pNew[0]));
 if( pNew==0 ) return 1;
 }
 p->fts5yystack = pNew;
 p->fts5yytos = &p->fts5yystack[idx];
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sStack grows from %d to %d entries.\n",
 fts5yyTracePrompt, oldSize, newSize);
 }
#endif
 p->fts5yystackEnd = &p->fts5yystack[newSize-1];
 return 0;
}
#endif /* fts5YYGROWABLESTACK */

#if !fts5YYGROWABLESTACK
/* For builds that do no have a growable stack, fts5yyGrowStack always
** returns an error.
*/
# define fts5yyGrowStack(X) 1
#endif

/* Datatype of the argument to the memory allocated passed as the
** second argument to sqlite3Fts5ParserAlloc() below. This can be changed by
** putting an appropriate #define in the %include section of the input
** grammar.
*/
#ifndef fts5YYMALLOCARGTYPE
# define fts5YYMALLOCARGTYPE size_t
#endif

/* Initialize a new parser that has already been allocated.
*/
static void sqlite3Fts5ParserInit(void *fts5yypRawParser sqlite3Fts5ParserCTX_PDECL){
 fts5yyParser *fts5yypParser = (fts5yyParser*)fts5yypRawParser;
 sqlite3Fts5ParserCTX_STORE
#ifdef fts5YYTRACKMAXSTACKDEPTH
 fts5yypParser->fts5yyhwm = 0;
#endif
 fts5yypParser->fts5yystack = fts5yypParser->fts5yystk0;
 fts5yypParser->fts5yystackEnd = &fts5yypParser->fts5yystack[fts5YYSTACKDEPTH-1];
#ifndef fts5YYNOERRORRECOVERY
 fts5yypParser->fts5yyerrcnt = -1;
#endif
 fts5yypParser->fts5yytos = fts5yypParser->fts5yystack;
 fts5yypParser->fts5yystack[0].stateno = 0;
 fts5yypParser->fts5yystack[0].major = 0;
}

#ifndef sqlite3Fts5Parser_ENGINEALWAYSONSTACK
/*
** This function allocates a new parser.
** The only argument is a pointer to a function which works like
** malloc.
**
** Inputs:
** A pointer to the function used to allocate memory.
**
** Outputs:
** A pointer to a parser. This pointer is used in subsequent calls
** to sqlite3Fts5Parser and sqlite3Fts5ParserFree.
*/
static void *sqlite3Fts5ParserAlloc(void *(*mallocProc)(fts5YYMALLOCARGTYPE) sqlite3Fts5ParserCTX_PDECL){
 fts5yyParser *fts5yypParser;
 fts5yypParser = (fts5yyParser*)(*mallocProc)( (fts5YYMALLOCARGTYPE)sizeof(fts5yyParser) );
 if( fts5yypParser ){
 sqlite3Fts5ParserCTX_STORE
 sqlite3Fts5ParserInit(fts5yypParser sqlite3Fts5ParserCTX_PARAM);
 }
 return (void*)fts5yypParser;
}
#endif /* sqlite3Fts5Parser_ENGINEALWAYSONSTACK */

/* The following function deletes the "minor type" or semantic value
** associated with a symbol. The symbol can be either a terminal
** or nonterminal. "fts5yymajor" is the symbol code, and "fts5yypminor" is
** a pointer to the value to be deleted. The code used to do the
** deletions is derived from the %destructor and/or %token_destructor
** directives of the input grammar.
*/
static void fts5yy_destructor(
 fts5yyParser *fts5yypParser, /* The parser */
 fts5YYCODETYPE fts5yymajor, /* Type code for object to destroy */
 fts5YYMINORTYPE *fts5yypminor /* The object to be destroyed */
){
 sqlite3Fts5ParserARG_FETCH
 sqlite3Fts5ParserCTX_FETCH
 switch( fts5yymajor ){
 /* Here is inserted the actions which take place when a
 ** terminal or non-terminal is destroyed. This can happen
 ** when the symbol is popped from the stack during a
 ** reduce or during error processing or when a parser is
 ** being destroyed before it is finished parsing.
 **
 ** Note: during a reduce, the only symbols destroyed are those
 ** which appear on the RHS of the rule, but which are *not* used
 ** inside the C code.
 */
/********* Begin destructor definitions ***************************************/
 case 16: /* input */
{
#line 83 "fts5parse.y"
(void)pParse;
#line 606 "fts5parse.sql"
}
 break;
 case 17: /* expr */
 case 18: /* cnearset */
 case 19: /* exprlist */
{
#line 89 "fts5parse.y"
sqlite3Fts5ParseNodeFree((fts5yypminor->fts5yy24));
#line 615 "fts5parse.sql"
}
 break;
 case 20: /* colset */
 case 21: /* colsetlist */
{
#line 93 "fts5parse.y"
sqlite3_free((fts5yypminor->fts5yy11));
#line 623 "fts5parse.sql"
}
 break;
 case 22: /* nearset */
 case 23: /* nearphrases */
{
#line 148 "fts5parse.y"
sqlite3Fts5ParseNearsetFree((fts5yypminor->fts5yy46));
#line 631 "fts5parse.sql"
}
 break;
 case 24: /* phrase */
{
#line 183 "fts5parse.y"
sqlite3Fts5ParsePhraseFree((fts5yypminor->fts5yy53));
#line 638 "fts5parse.sql"
}
 break;
/********* End destructor definitions *****************************************/
 default: break; /* If no destructor action specified: do nothing */
 }
}

/*
** Pop the parser's stack once.
**
** If there is a destructor routine associated with the token which
** is popped from the stack, then call it.
*/
static void fts5yy_pop_parser_stack(fts5yyParser *pParser){
 fts5yyStackEntry *fts5yytos;
 assert( pParser->fts5yytos!=0 );
 assert( pParser->fts5yytos > pParser->fts5yystack );
 fts5yytos = pParser->fts5yytos--;
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sPopping %s\n",
 fts5yyTracePrompt,
 fts5yyTokenName[fts5yytos->major]);
 }
#endif
 fts5yy_destructor(pParser, fts5yytos->major, &fts5yytos->minor);
}

/*
** Clear all secondary memory allocations from the parser
*/
static void sqlite3Fts5ParserFinalize(void *p){
 fts5yyParser *pParser = (fts5yyParser*)p;

 /* In-lined version of calling fts5yy_pop_parser_stack() for each
 ** element left in the stack */
 fts5yyStackEntry *fts5yytos = pParser->fts5yytos;
 while( fts5yytos>pParser->fts5yystack ){
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sPopping %s\n",
 fts5yyTracePrompt,
 fts5yyTokenName[fts5yytos->major]);
 }
#endif
 if( fts5yytos->major>=fts5YY_MIN_DSTRCTR ){
 fts5yy_destructor(pParser, fts5yytos->major, &fts5yytos->minor);
 }
 fts5yytos--;
 }

#if fts5YYGROWABLESTACK
 if( pParser->fts5yystack!=pParser->fts5yystk0 ) fts5YYFREE(pParser->fts5yystack);
#endif
}

#ifndef sqlite3Fts5Parser_ENGINEALWAYSONSTACK
/*
** Deallocate and destroy a parser. Destructors are called for
** all stack elements before shutting the parser down.
**
** If the fts5YYPARSEFREENEVERNULL macro exists (for example because it
** is defined in a %include section of the input grammar) then it is
** assumed that the input pointer is never NULL.
*/
static void sqlite3Fts5ParserFree(
 void *p, /* The parser to be deleted */
 void (*freeProc)(void*) /* Function used to reclaim memory */
){
#ifndef fts5YYPARSEFREENEVERNULL
 if( p==0 ) return;
#endif
 sqlite3Fts5ParserFinalize(p);
 (*freeProc)(p);
}
#endif /* sqlite3Fts5Parser_ENGINEALWAYSONSTACK */

/*
** Return the peak depth of the stack for a parser.
*/
#ifdef fts5YYTRACKMAXSTACKDEPTH
static int sqlite3Fts5ParserStackPeak(void *p){
 fts5yyParser *pParser = (fts5yyParser*)p;
 return pParser->fts5yyhwm;
}
#endif

/* This array of booleans keeps track of the parser statement
** coverage. The element fts5yycoverage[X][Y] is set when the parser
** is in state X and has a lookahead token Y. In a well-tested
** systems, every element of this matrix should end up being set.
*/
#if defined(fts5YYCOVERAGE)
static unsigned char fts5yycoverage[fts5YYNSTATE][fts5YYNFTS5TOKEN];
#endif

/*
** Write into out a description of every state/lookahead combination that
**
** (1) has not been used by the parser, and
** (2) is not a syntax error.
**
** Return the number of missed state/lookahead combinations.
*/
#if defined(fts5YYCOVERAGE)
static int sqlite3Fts5ParserCoverage(FILE *out){
 int stateno, iLookAhead, i;
 int nMissed = 0;
 for(stateno=0; stateno<fts5YYNSTATE; stateno++){
 i = fts5yy_shift_ofst[stateno];
 for(iLookAhead=0; iLookAhead<fts5YYNFTS5TOKEN; iLookAhead++){
 if( fts5yy_lookahead[i+iLookAhead]!=iLookAhead ) continue;
 if( fts5yycoverage[stateno][iLookAhead]==0 ) nMissed++;
 if( out ){
 fprintf(out,"State %d lookahead %s %s\n", stateno,
 fts5yyTokenName[iLookAhead],
 fts5yycoverage[stateno][iLookAhead] ? "ok" : "missed");
 }
 }
 }
 return nMissed;
}
#endif

/*
** Find the appropriate action for a parser given the terminal
** look-ahead token iLookAhead.
*/
static fts5YYACTIONTYPE fts5yy_find_shift_action(
 fts5YYCODETYPE iLookAhead, /* The look-ahead token */
 fts5YYACTIONTYPE stateno /* Current state number */
){
 int i;

 if( stateno>fts5YY_MAX_SHIFT ) return stateno;
 assert( stateno <= fts5YY_SHIFT_COUNT );
#if defined(fts5YYCOVERAGE)
 fts5yycoverage[stateno][iLookAhead] = 1;
#endif
 do{
 i = fts5yy_shift_ofst[stateno];
 assert( i>=0 );
 assert( i<=fts5YY_ACTTAB_COUNT );
 assert( i+fts5YYNFTS5TOKEN<=(int)fts5YY_NLOOKAHEAD );
 assert( iLookAhead!=fts5YYNOCODE );
 assert( iLookAhead < fts5YYNFTS5TOKEN );
 i += iLookAhead;
 assert( i<(int)fts5YY_NLOOKAHEAD );
 if( fts5yy_lookahead[i]!=iLookAhead ){
#ifdef fts5YYFALLBACK
 fts5YYCODETYPE iFallback; /* Fallback token */
 assert( iLookAhead<sizeof(fts5yyFallback)/sizeof(fts5yyFallback[0]) );
 iFallback = fts5yyFallback[iLookAhead];
 if( iFallback!=0 ){
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE, "%sFALLBACK %s => %s\n",
 fts5yyTracePrompt, fts5yyTokenName[iLookAhead], fts5yyTokenName[iFallback]);
 }
#endif
 assert( fts5yyFallback[iFallback]==0 ); /* Fallback loop must terminate */
 iLookAhead = iFallback;
 continue;
 }
#endif
#ifdef fts5YYWILDCARD
 {
 int j = i - iLookAhead + fts5YYWILDCARD;
 assert( j<(int)(sizeof(fts5yy_lookahead)/sizeof(fts5yy_lookahead[0])) );
 if( fts5yy_lookahead[j]==fts5YYWILDCARD && iLookAhead>0 ){
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE, "%sWILDCARD %s => %s\n",
 fts5yyTracePrompt, fts5yyTokenName[iLookAhead],
 fts5yyTokenName[fts5YYWILDCARD]);
 }
#endif /* NDEBUG */
 return fts5yy_action[j];
 }
 }
#endif /* fts5YYWILDCARD */
 return fts5yy_default[stateno];
 }else{
 assert( i>=0 && i<(int)(sizeof(fts5yy_action)/sizeof(fts5yy_action[0])) );
 return fts5yy_action[i];
 }
 }while(1);
}

/*
** Find the appropriate action for a parser given the non-terminal
** look-ahead token iLookAhead.
*/
static fts5YYACTIONTYPE fts5yy_find_reduce_action(
 fts5YYACTIONTYPE stateno, /* Current state number */
 fts5YYCODETYPE iLookAhead /* The look-ahead token */
){
 int i;
#ifdef fts5YYERRORSYMBOL
 if( stateno>fts5YY_REDUCE_COUNT ){
 return fts5yy_default[stateno];
 }
#else
 assert( stateno<=fts5YY_REDUCE_COUNT );
#endif
 i = fts5yy_reduce_ofst[stateno];
 assert( iLookAhead!=fts5YYNOCODE );
 i += iLookAhead;
#ifdef fts5YYERRORSYMBOL
 if( i<0 || i>=fts5YY_ACTTAB_COUNT || fts5yy_lookahead[i]!=iLookAhead ){
 return fts5yy_default[stateno];
 }
#else
 assert( i>=0 && i<fts5YY_ACTTAB_COUNT );
 assert( fts5yy_lookahead[i]==iLookAhead );
#endif
 return fts5yy_action[i];
}

/*
** The following routine is called if the stack overflows.
*/
static void fts5yyStackOverflow(fts5yyParser *fts5yypParser){
 sqlite3Fts5ParserARG_FETCH
 sqlite3Fts5ParserCTX_FETCH
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sStack Overflow!\n",fts5yyTracePrompt);
 }
#endif
 while( fts5yypParser->fts5yytos>fts5yypParser->fts5yystack ) fts5yy_pop_parser_stack(fts5yypParser);
 /* Here code is inserted which will execute if the parser
 ** stack every overflows */
/******** Begin %stack_overflow code ******************************************/
#line 36 "fts5parse.y"

 sqlite3Fts5ParseError(pParse, "fts5: parser stack overflow");
#line 876 "fts5parse.sql"
/******** End %stack_overflow code ********************************************/
 sqlite3Fts5ParserARG_STORE /* Suppress warning about unused %extra_argument var */
 sqlite3Fts5ParserCTX_STORE
}

/*
** Print tracing information for a SHIFT action
*/
#ifndef NDEBUG
static void fts5yyTraceShift(fts5yyParser *fts5yypParser, int fts5yyNewState, const char *zTag){
 if( fts5yyTraceFILE ){
 if( fts5yyNewState<fts5YYNSTATE ){
 fprintf(fts5yyTraceFILE,"%s%s '%s', go to state %d\n",
 fts5yyTracePrompt, zTag, fts5yyTokenName[fts5yypParser->fts5yytos->major],
 fts5yyNewState);
 }else{
 fprintf(fts5yyTraceFILE,"%s%s '%s', pending reduce %d\n",
 fts5yyTracePrompt, zTag, fts5yyTokenName[fts5yypParser->fts5yytos->major],
 fts5yyNewState - fts5YY_MIN_REDUCE);
 }
 }
}
#else
# define fts5yyTraceShift(X,Y,Z)
#endif

/*
** Perform a shift action.
*/
static void fts5yy_shift(
 fts5yyParser *fts5yypParser, /* The parser to be shifted */
 fts5YYACTIONTYPE fts5yyNewState, /* The new state to shift in */
 fts5YYCODETYPE fts5yyMajor, /* The major token to shift in */
 sqlite3Fts5ParserFTS5TOKENTYPE fts5yyMinor /* The minor token to shift in */
){
 fts5yyStackEntry *fts5yytos;
 fts5yypParser->fts5yytos++;
#ifdef fts5YYTRACKMAXSTACKDEPTH
 if( (int)(fts5yypParser->fts5yytos - fts5yypParser->fts5yystack)>fts5yypParser->fts5yyhwm ){
 fts5yypParser->fts5yyhwm++;
 assert( fts5yypParser->fts5yyhwm == (int)(fts5yypParser->fts5yytos - fts5yypParser->fts5yystack) );
 }
#endif
 fts5yytos = fts5yypParser->fts5yytos;
 if( fts5yytos>fts5yypParser->fts5yystackEnd ){
 if( fts5yyGrowStack(fts5yypParser) ){
 fts5yypParser->fts5yytos--;
 fts5yyStackOverflow(fts5yypParser);
 return;
 }
 fts5yytos = fts5yypParser->fts5yytos;
 assert( fts5yytos <= fts5yypParser->fts5yystackEnd );
 }
 if( fts5yyNewState > fts5YY_MAX_SHIFT ){
 fts5yyNewState += fts5YY_MIN_REDUCE - fts5YY_MIN_SHIFTREDUCE;
 }
 fts5yytos->stateno = fts5yyNewState;
 fts5yytos->major = fts5yyMajor;
 fts5yytos->minor.fts5yy0 = fts5yyMinor;
 fts5yyTraceShift(fts5yypParser, fts5yyNewState, "Shift");
}

/* For rule J, fts5yyRuleInfoLhs[J] contains the symbol on the left-hand side
** of that rule */
static const fts5YYCODETYPE fts5yyRuleInfoLhs[] = {
 16, /* (0) input ::= expr */
 20, /* (1) colset ::= MINUS LCP colsetlist RCP */
 20, /* (2) colset ::= LCP colsetlist RCP */
 20, /* (3) colset ::= STRING */
 20, /* (4) colset ::= MINUS STRING */
 21, /* (5) colsetlist ::= colsetlist STRING */
 21, /* (6) colsetlist ::= STRING */
 17, /* (7) expr ::= expr AND expr */
 17, /* (8) expr ::= expr OR expr */
 17, /* (9) expr ::= expr NOT expr */
 17, /* (10) expr ::= colset COLON LP expr RP */
 17, /* (11) expr ::= LP expr RP */
 17, /* (12) expr ::= exprlist */
 19, /* (13) exprlist ::= cnearset */
 19, /* (14) exprlist ::= exprlist cnearset */
 18, /* (15) cnearset ::= nearset */
 18, /* (16) cnearset ::= colset COLON nearset */
 22, /* (17) nearset ::= phrase */
 22, /* (18) nearset ::= CARET phrase */
 22, /* (19) nearset ::= STRING LP nearphrases neardist_opt RP */
 23, /* (20) nearphrases ::= phrase */
 23, /* (21) nearphrases ::= nearphrases phrase */
 25, /* (22) neardist_opt ::= */
 25, /* (23) neardist_opt ::= COMMA STRING */
 24, /* (24) phrase ::= phrase PLUS STRING star_opt */
 24, /* (25) phrase ::= STRING star_opt */
 26, /* (26) star_opt ::= STAR */
 26, /* (27) star_opt ::= */
};

/* For rule J, fts5yyRuleInfoNRhs[J] contains the negative of the number
** of symbols on the right-hand side of that rule. */
static const signed char fts5yyRuleInfoNRhs[] = {
 -1, /* (0) input ::= expr */
 -4, /* (1) colset ::= MINUS LCP colsetlist RCP */
 -3, /* (2) colset ::= LCP colsetlist RCP */
 -1, /* (3) colset ::= STRING */
 -2, /* (4) colset ::= MINUS STRING */
 -2, /* (5) colsetlist ::= colsetlist STRING */
 -1, /* (6) colsetlist ::= STRING */
 -3, /* (7) expr ::= expr AND expr */
 -3, /* (8) expr ::= expr OR expr */
 -3, /* (9) expr ::= expr NOT expr */
 -5, /* (10) expr ::= colset COLON LP expr RP */
 -3, /* (11) expr ::= LP expr RP */
 -1, /* (12) expr ::= exprlist */
 -1, /* (13) exprlist ::= cnearset */
 -2, /* (14) exprlist ::= exprlist cnearset */
 -1, /* (15) cnearset ::= nearset */
 -3, /* (16) cnearset ::= colset COLON nearset */
 -1, /* (17) nearset ::= phrase */
 -2, /* (18) nearset ::= CARET phrase */
 -5, /* (19) nearset ::= STRING LP nearphrases neardist_opt RP */
 -1, /* (20) nearphrases ::= phrase */
 -2, /* (21) nearphrases ::= nearphrases phrase */
 0, /* (22) neardist_opt ::= */
 -2, /* (23) neardist_opt ::= COMMA STRING */
 -4, /* (24) phrase ::= phrase PLUS STRING star_opt */
 -2, /* (25) phrase ::= STRING star_opt */
 -1, /* (26) star_opt ::= STAR */
 0, /* (27) star_opt ::= */
};

static void fts5yy_accept(fts5yyParser*); /* Forward Declaration */

/*
** Perform a reduce action and the shift that must immediately
** follow the reduce.
**
** The fts5yyLookahead and fts5yyLookaheadToken parameters provide reduce actions
** access to the lookahead token (if any). The fts5yyLookahead will be fts5YYNOCODE
** if the lookahead token has already been consumed. As this procedure is
** only called from one place, optimizing compilers will in-line it, which
** means that the extra parameters have no performance impact.
*/
static fts5YYACTIONTYPE fts5yy_reduce(
 fts5yyParser *fts5yypParser, /* The parser */
 unsigned int fts5yyruleno, /* Number of the rule by which to reduce */
 int fts5yyLookahead, /* Lookahead token, or fts5YYNOCODE if none */
 sqlite3Fts5ParserFTS5TOKENTYPE fts5yyLookaheadToken /* Value of the lookahead token */
 sqlite3Fts5ParserCTX_PDECL /* %extra_context */
){
 int fts5yygoto; /* The next state */
 fts5YYACTIONTYPE fts5yyact; /* The next action */
 fts5yyStackEntry *fts5yymsp; /* The top of the parser's stack */
 int fts5yysize; /* Amount to pop the stack */
 sqlite3Fts5ParserARG_FETCH
 (void)fts5yyLookahead;
 (void)fts5yyLookaheadToken;
 fts5yymsp = fts5yypParser->fts5yytos;

 switch( fts5yyruleno ){
 /* Beginning here are the reduction cases. A typical example
 ** follows:
 ** case 0:
 ** #line <lineno> <grammarfile>
 ** { ... } // User supplied code
 ** #line <lineno> <thisfile>
 ** break;
 */
/********** Begin reduce actions **********************************************/
 fts5YYMINORTYPE fts5yylhsminor;
 case 0: /* input ::= expr */
#line 82 "fts5parse.y"
{ sqlite3Fts5ParseFinished(pParse, fts5yymsp[0].minor.fts5yy24); }
#line 1047 "fts5parse.sql"
 break;
 case 1: /* colset ::= MINUS LCP colsetlist RCP */
#line 97 "fts5parse.y"
{
 fts5yymsp[-3].minor.fts5yy11 = sqlite3Fts5ParseColsetInvert(pParse, fts5yymsp[-1].minor.fts5yy11);
}
#line 1054 "fts5parse.sql"
 break;
 case 2: /* colset ::= LCP colsetlist RCP */
#line 100 "fts5parse.y"
{ fts5yymsp[-2].minor.fts5yy11 = fts5yymsp[-1].minor.fts5yy11; }
#line 1059 "fts5parse.sql"
 break;
 case 3: /* colset ::= STRING */
#line 101 "fts5parse.y"
{
 fts5yylhsminor.fts5yy11 = sqlite3Fts5ParseColset(pParse, 0, &fts5yymsp[0].minor.fts5yy0);
}
#line 1066 "fts5parse.sql"
 fts5yymsp[0].minor.fts5yy11 = fts5yylhsminor.fts5yy11;
 break;
 case 4: /* colset ::= MINUS STRING */
#line 104 "fts5parse.y"
{
 fts5yymsp[-1].minor.fts5yy11 = sqlite3Fts5ParseColset(pParse, 0, &fts5yymsp[0].minor.fts5yy0);
 fts5yymsp[-1].minor.fts5yy11 = sqlite3Fts5ParseColsetInvert(pParse, fts5yymsp[-1].minor.fts5yy11);
}
#line 1075 "fts5parse.sql"
 break;
 case 5: /* colsetlist ::= colsetlist STRING */
#line 109 "fts5parse.y"
{
 fts5yylhsminor.fts5yy11 = sqlite3Fts5ParseColset(pParse, fts5yymsp[-1].minor.fts5yy11, &fts5yymsp[0].minor.fts5yy0); }
#line 1081 "fts5parse.sql"
 fts5yymsp[-1].minor.fts5yy11 = fts5yylhsminor.fts5yy11;
 break;
 case 6: /* colsetlist ::= STRING */
#line 111 "fts5parse.y"
{
 fts5yylhsminor.fts5yy11 = sqlite3Fts5ParseColset(pParse, 0, &fts5yymsp[0].minor.fts5yy0);
}
#line 1089 "fts5parse.sql"
 fts5yymsp[0].minor.fts5yy11 = fts5yylhsminor.fts5yy11;
 break;
 case 7: /* expr ::= expr AND expr */
#line 115 "fts5parse.y"
{
 fts5yylhsminor.fts5yy24 = sqlite3Fts5ParseNode(pParse, FTS5_AND, fts5yymsp[-2].minor.fts5yy24, fts5yymsp[0].minor.fts5yy24, 0);
}
#line 1097 "fts5parse.sql"
 fts5yymsp[-2].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 8: /* expr ::= expr OR expr */
#line 118 "fts5parse.y"
{
 fts5yylhsminor.fts5yy24 = sqlite3Fts5ParseNode(pParse, FTS5_OR, fts5yymsp[-2].minor.fts5yy24, fts5yymsp[0].minor.fts5yy24, 0);
}
#line 1105 "fts5parse.sql"
 fts5yymsp[-2].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 9: /* expr ::= expr NOT expr */
#line 121 "fts5parse.y"
{
 fts5yylhsminor.fts5yy24 = sqlite3Fts5ParseNode(pParse, FTS5_NOT, fts5yymsp[-2].minor.fts5yy24, fts5yymsp[0].minor.fts5yy24, 0);
}
#line 1113 "fts5parse.sql"
 fts5yymsp[-2].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 10: /* expr ::= colset COLON LP expr RP */
#line 125 "fts5parse.y"
{
 sqlite3Fts5ParseSetColset(pParse, fts5yymsp[-1].minor.fts5yy24, fts5yymsp[-4].minor.fts5yy11);
 fts5yylhsminor.fts5yy24 = fts5yymsp[-1].minor.fts5yy24;
}
#line 1122 "fts5parse.sql"
 fts5yymsp[-4].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 11: /* expr ::= LP expr RP */
#line 129 "fts5parse.y"
{fts5yymsp[-2].minor.fts5yy24 = fts5yymsp[-1].minor.fts5yy24;}
#line 1128 "fts5parse.sql"
 break;
 case 12: /* expr ::= exprlist */
 case 13: /* exprlist ::= cnearset */ fts5yytestcase(fts5yyruleno==13);
#line 130 "fts5parse.y"
{fts5yylhsminor.fts5yy24 = fts5yymsp[0].minor.fts5yy24;}
#line 1134 "fts5parse.sql"
 fts5yymsp[0].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 14: /* exprlist ::= exprlist cnearset */
#line 133 "fts5parse.y"
{
 fts5yylhsminor.fts5yy24 = sqlite3Fts5ParseImplicitAnd(pParse, fts5yymsp[-1].minor.fts5yy24, fts5yymsp[0].minor.fts5yy24);
}
#line 1142 "fts5parse.sql"
 fts5yymsp[-1].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 15: /* cnearset ::= nearset */
#line 137 "fts5parse.y"
{
 fts5yylhsminor.fts5yy24 = sqlite3Fts5ParseNode(pParse, FTS5_STRING, 0, 0, fts5yymsp[0].minor.fts5yy46);
}
#line 1150 "fts5parse.sql"
 fts5yymsp[0].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 16: /* cnearset ::= colset COLON nearset */
#line 140 "fts5parse.y"
{
 fts5yylhsminor.fts5yy24 = sqlite3Fts5ParseNode(pParse, FTS5_STRING, 0, 0, fts5yymsp[0].minor.fts5yy46);
 sqlite3Fts5ParseSetColset(pParse, fts5yylhsminor.fts5yy24, fts5yymsp[-2].minor.fts5yy11);
}
#line 1159 "fts5parse.sql"
 fts5yymsp[-2].minor.fts5yy24 = fts5yylhsminor.fts5yy24;
 break;
 case 17: /* nearset ::= phrase */
#line 151 "fts5parse.y"
{ fts5yylhsminor.fts5yy46 = sqlite3Fts5ParseNearset(pParse, 0, fts5yymsp[0].minor.fts5yy53); }
#line 1165 "fts5parse.sql"
 fts5yymsp[0].minor.fts5yy46 = fts5yylhsminor.fts5yy46;
 break;
 case 18: /* nearset ::= CARET phrase */
#line 152 "fts5parse.y"
{
 sqlite3Fts5ParseSetCaret(fts5yymsp[0].minor.fts5yy53);
 fts5yymsp[-1].minor.fts5yy46 = sqlite3Fts5ParseNearset(pParse, 0, fts5yymsp[0].minor.fts5yy53);
}
#line 1174 "fts5parse.sql"
 break;
 case 19: /* nearset ::= STRING LP nearphrases neardist_opt RP */
#line 156 "fts5parse.y"
{
 sqlite3Fts5ParseNear(pParse, &fts5yymsp[-4].minor.fts5yy0);
 sqlite3Fts5ParseSetDistance(pParse, fts5yymsp[-2].minor.fts5yy46, &fts5yymsp[-1].minor.fts5yy0);
 fts5yylhsminor.fts5yy46 = fts5yymsp[-2].minor.fts5yy46;
}
#line 1183 "fts5parse.sql"
 fts5yymsp[-4].minor.fts5yy46 = fts5yylhsminor.fts5yy46;
 break;
 case 20: /* nearphrases ::= phrase */
#line 162 "fts5parse.y"
{
 fts5yylhsminor.fts5yy46 = sqlite3Fts5ParseNearset(pParse, 0, fts5yymsp[0].minor.fts5yy53);
}
#line 1191 "fts5parse.sql"
 fts5yymsp[0].minor.fts5yy46 = fts5yylhsminor.fts5yy46;
 break;
 case 21: /* nearphrases ::= nearphrases phrase */
#line 165 "fts5parse.y"
{
 fts5yylhsminor.fts5yy46 = sqlite3Fts5ParseNearset(pParse, fts5yymsp[-1].minor.fts5yy46, fts5yymsp[0].minor.fts5yy53);
}
#line 1199 "fts5parse.sql"
 fts5yymsp[-1].minor.fts5yy46 = fts5yylhsminor.fts5yy46;
 break;
 case 22: /* neardist_opt ::= */
#line 172 "fts5parse.y"
{ fts5yymsp[1].minor.fts5yy0.p = 0; fts5yymsp[1].minor.fts5yy0.n = 0; }
#line 1205 "fts5parse.sql"
 break;
 case 23: /* neardist_opt ::= COMMA STRING */
#line 173 "fts5parse.y"
{ fts5yymsp[-1].minor.fts5yy0 = fts5yymsp[0].minor.fts5yy0; }
#line 1210 "fts5parse.sql"
 break;
 case 24: /* phrase ::= phrase PLUS STRING star_opt */
#line 185 "fts5parse.y"
{
 fts5yylhsminor.fts5yy53 = sqlite3Fts5ParseTerm(pParse, fts5yymsp[-3].minor.fts5yy53, &fts5yymsp[-1].minor.fts5yy0, fts5yymsp[0].minor.fts5yy4);
}
#line 1217 "fts5parse.sql"
 fts5yymsp[-3].minor.fts5yy53 = fts5yylhsminor.fts5yy53;
 break;
 case 25: /* phrase ::= STRING star_opt */
#line 188 "fts5parse.y"
{
 fts5yylhsminor.fts5yy53 = sqlite3Fts5ParseTerm(pParse, 0, &fts5yymsp[-1].minor.fts5yy0, fts5yymsp[0].minor.fts5yy4);
}
#line 1225 "fts5parse.sql"
 fts5yymsp[-1].minor.fts5yy53 = fts5yylhsminor.fts5yy53;
 break;
 case 26: /* star_opt ::= STAR */
#line 196 "fts5parse.y"
{ fts5yymsp[0].minor.fts5yy4 = 1; }
#line 1231 "fts5parse.sql"
 break;
 case 27: /* star_opt ::= */
#line 197 "fts5parse.y"
{ fts5yymsp[1].minor.fts5yy4 = 0; }
#line 1236 "fts5parse.sql"
 break;
 default:
 break;
/********** End reduce actions ************************************************/
 };
 assert( fts5yyruleno<sizeof(fts5yyRuleInfoLhs)/sizeof(fts5yyRuleInfoLhs[0]) );
 fts5yygoto = fts5yyRuleInfoLhs[fts5yyruleno];
 fts5yysize = fts5yyRuleInfoNRhs[fts5yyruleno];
 fts5yyact = fts5yy_find_reduce_action(fts5yymsp[fts5yysize].stateno,(fts5YYCODETYPE)fts5yygoto);

 /* There are no SHIFTREDUCE actions on nonterminals because the table
 ** generator has simplified them to pure REDUCE actions. */
 assert( !(fts5yyact>fts5YY_MAX_SHIFT && fts5yyact<=fts5YY_MAX_SHIFTREDUCE) );

 /* It is not possible for a REDUCE to be followed by an error */
 assert( fts5yyact!=fts5YY_ERROR_ACTION );

 fts5yymsp += fts5yysize+1;
 fts5yypParser->fts5yytos = fts5yymsp;
 fts5yymsp->stateno = (fts5YYACTIONTYPE)fts5yyact;
 fts5yymsp->major = (fts5YYCODETYPE)fts5yygoto;
 fts5yyTraceShift(fts5yypParser, fts5yyact, "... then shift");
 return fts5yyact;
}

/*
** The following code executes when the parse fails
*/
#ifndef fts5YYNOERRORRECOVERY
static void fts5yy_parse_failed(
 fts5yyParser *fts5yypParser /* The parser */
){
 sqlite3Fts5ParserARG_FETCH
 sqlite3Fts5ParserCTX_FETCH
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sFail!\n",fts5yyTracePrompt);
 }
#endif
 while( fts5yypParser->fts5yytos>fts5yypParser->fts5yystack ) fts5yy_pop_parser_stack(fts5yypParser);
 /* Here code is inserted which will be executed whenever the
 ** parser fails */
/************ Begin %parse_failure code ***************************************/
/************ End %parse_failure code *****************************************/
 sqlite3Fts5ParserARG_STORE /* Suppress warning about unused %extra_argument variable */
 sqlite3Fts5ParserCTX_STORE
}
#endif /* fts5YYNOERRORRECOVERY */

/*
** The following code executes when a syntax error first occurs.
*/
static void fts5yy_syntax_error(
 fts5yyParser *fts5yypParser, /* The parser */
 int fts5yymajor, /* The major type of the error token */
 sqlite3Fts5ParserFTS5TOKENTYPE fts5yyminor /* The minor type of the error token */
){
 sqlite3Fts5ParserARG_FETCH
 sqlite3Fts5ParserCTX_FETCH
#define FTS5TOKEN fts5yyminor
/************ Begin %syntax_error code ****************************************/
#line 30 "fts5parse.y"

 UNUSED_PARAM(fts5yymajor); /* Silence a compiler warning */
 sqlite3Fts5ParseError(
 pParse, "fts5: syntax error near \"%.*s\"",FTS5TOKEN.n,FTS5TOKEN.p
 );
#line 1304 "fts5parse.sql"
/************ End %syntax_error code ******************************************/
 sqlite3Fts5ParserARG_STORE /* Suppress warning about unused %extra_argument variable */
 sqlite3Fts5ParserCTX_STORE
}

/*
** The following is executed when the parser accepts
*/
static void fts5yy_accept(
 fts5yyParser *fts5yypParser /* The parser */
){
 sqlite3Fts5ParserARG_FETCH
 sqlite3Fts5ParserCTX_FETCH
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sAccept!\n",fts5yyTracePrompt);
 }
#endif
#ifndef fts5YYNOERRORRECOVERY
 fts5yypParser->fts5yyerrcnt = -1;
#endif
 assert( fts5yypParser->fts5yytos==fts5yypParser->fts5yystack );
 /* Here code is inserted which will be executed whenever the
 ** parser accepts */
/*********** Begin %parse_accept code *****************************************/
/*********** End %parse_accept code *******************************************/
 sqlite3Fts5ParserARG_STORE /* Suppress warning about unused %extra_argument variable */
 sqlite3Fts5ParserCTX_STORE
}

/* The main parser program.
** The first argument is a pointer to a structure obtained from
** "sqlite3Fts5ParserAlloc" which describes the current state of the parser.
** The second argument is the major token number. The third is
** the minor token. The fourth optional argument is whatever the
** user wants (and specified in the grammar) and is available for
** use by the action routines.
**
** Inputs:
** <ul>
** <li> A pointer to the parser (an opaque structure.)
** <li> The major token number.
** <li> The minor token number.
** <li> An option argument of a grammar-specified type.
** </ul>
**
** Outputs:
** None.
*/
static void sqlite3Fts5Parser(
 void *fts5yyp, /* The parser */
 int fts5yymajor, /* The major token code number */
 sqlite3Fts5ParserFTS5TOKENTYPE fts5yyminor /* The value for the token */
 sqlite3Fts5ParserARG_PDECL /* Optional %extra_argument parameter */
){
 fts5YYMINORTYPE fts5yyminorunion;
 fts5YYACTIONTYPE fts5yyact; /* The parser action. */
#if !defined(fts5YYERRORSYMBOL) && !defined(fts5YYNOERRORRECOVERY)
 int fts5yyendofinput; /* True if we are at the end of input */
#endif
#ifdef fts5YYERRORSYMBOL
 int fts5yyerrorhit = 0; /* True if fts5yymajor has invoked an error */
#endif
 fts5yyParser *fts5yypParser = (fts5yyParser*)fts5yyp; /* The parser */
 sqlite3Fts5ParserCTX_FETCH
 sqlite3Fts5ParserARG_STORE

 assert( fts5yypParser->fts5yytos!=0 );
#if !defined(fts5YYERRORSYMBOL) && !defined(fts5YYNOERRORRECOVERY)
 fts5yyendofinput = (fts5yymajor==0);
#endif

 fts5yyact = fts5yypParser->fts5yytos->stateno;
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 if( fts5yyact < fts5YY_MIN_REDUCE ){
 fprintf(fts5yyTraceFILE,"%sInput '%s' in state %d\n",
 fts5yyTracePrompt,fts5yyTokenName[fts5yymajor],fts5yyact);
 }else{
 fprintf(fts5yyTraceFILE,"%sInput '%s' with pending reduce %d\n",
 fts5yyTracePrompt,fts5yyTokenName[fts5yymajor],fts5yyact-fts5YY_MIN_REDUCE);
 }
 }
#endif

 while(1){ /* Exit by "break" */
 assert( fts5yypParser->fts5yytos>=fts5yypParser->fts5yystack );
 assert( fts5yyact==fts5yypParser->fts5yytos->stateno );
 fts5yyact = fts5yy_find_shift_action((fts5YYCODETYPE)fts5yymajor,fts5yyact);
 if( fts5yyact >= fts5YY_MIN_REDUCE ){
 unsigned int fts5yyruleno = fts5yyact - fts5YY_MIN_REDUCE; /* Reduce by this rule */
#ifndef NDEBUG
 assert( fts5yyruleno<(int)(sizeof(fts5yyRuleName)/sizeof(fts5yyRuleName[0])) );
 if( fts5yyTraceFILE ){
 int fts5yysize = fts5yyRuleInfoNRhs[fts5yyruleno];
 if( fts5yysize ){
 fprintf(fts5yyTraceFILE, "%sReduce %d [%s]%s, pop back to state %d.\n",
 fts5yyTracePrompt,
 fts5yyruleno, fts5yyRuleName[fts5yyruleno],
 fts5yyruleno<fts5YYNRULE_WITH_ACTION ? "" : " without external action",
 fts5yypParser->fts5yytos[fts5yysize].stateno);
 }else{
 fprintf(fts5yyTraceFILE, "%sReduce %d [%s]%s.\n",
 fts5yyTracePrompt, fts5yyruleno, fts5yyRuleName[fts5yyruleno],
 fts5yyruleno<fts5YYNRULE_WITH_ACTION ? "" : " without external action");
 }
 }
#endif /* NDEBUG */

 /* Check that the stack is large enough to grow by a single entry
 ** if the RHS of the rule is empty. This ensures that there is room
 ** enough on the stack to push the LHS value */
 if( fts5yyRuleInfoNRhs[fts5yyruleno]==0 ){
#ifdef fts5YYTRACKMAXSTACKDEPTH
 if( (int)(fts5yypParser->fts5yytos - fts5yypParser->fts5yystack)>fts5yypParser->fts5yyhwm ){
 fts5yypParser->fts5yyhwm++;
 assert( fts5yypParser->fts5yyhwm ==
 (int)(fts5yypParser->fts5yytos - fts5yypParser->fts5yystack));
 }
#endif
 if( fts5yypParser->fts5yytos>=fts5yypParser->fts5yystackEnd ){
 if( fts5yyGrowStack(fts5yypParser) ){
 fts5yyStackOverflow(fts5yypParser);
 break;
 }
 }
 }
 fts5yyact = fts5yy_reduce(fts5yypParser,fts5yyruleno,fts5yymajor,fts5yyminor sqlite3Fts5ParserCTX_PARAM);
 }else if( fts5yyact <= fts5YY_MAX_SHIFTREDUCE ){
 fts5yy_shift(fts5yypParser,fts5yyact,(fts5YYCODETYPE)fts5yymajor,fts5yyminor);
#ifndef fts5YYNOERRORRECOVERY
 fts5yypParser->fts5yyerrcnt--;
#endif
 break;
 }else if( fts5yyact==fts5YY_ACCEPT_ACTION ){
 fts5yypParser->fts5yytos--;
 fts5yy_accept(fts5yypParser);
 return;
 }else{
 assert( fts5yyact == fts5YY_ERROR_ACTION );
 fts5yyminorunion.fts5yy0 = fts5yyminor;
#ifdef fts5YYERRORSYMBOL
 int fts5yymx;
#endif
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sSyntax Error!\n",fts5yyTracePrompt);
 }
#endif
#ifdef fts5YYERRORSYMBOL
 /* A syntax error has occurred.
 ** The response to an error depends upon whether or not the
 ** grammar defines an error token "ERROR".
 **
 ** This is what we do if the grammar does define ERROR:
 **
 ** * Call the %syntax_error function.
 **
 ** * Begin popping the stack until we enter a state where
 ** it is legal to shift the error symbol, then shift
 ** the error symbol.
 **
 ** * Set the error count to three.
 **
 ** * Begin accepting and shifting new tokens. No new error
 ** processing will occur until three tokens have been
 ** shifted successfully.
 **
 */
 if( fts5yypParser->fts5yyerrcnt<0 ){
 fts5yy_syntax_error(fts5yypParser,fts5yymajor,fts5yyminor);
 }
 fts5yymx = fts5yypParser->fts5yytos->major;
 if( fts5yymx==fts5YYERRORSYMBOL || fts5yyerrorhit ){
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fprintf(fts5yyTraceFILE,"%sDiscard input token %s\n",
 fts5yyTracePrompt,fts5yyTokenName[fts5yymajor]);
 }
#endif
 fts5yy_destructor(fts5yypParser, (fts5YYCODETYPE)fts5yymajor, &fts5yyminorunion);
 fts5yymajor = fts5YYNOCODE;
 }else{
 while( fts5yypParser->fts5yytos > fts5yypParser->fts5yystack ){
 fts5yyact = fts5yy_find_reduce_action(fts5yypParser->fts5yytos->stateno,
 fts5YYERRORSYMBOL);
 if( fts5yyact<=fts5YY_MAX_SHIFTREDUCE ) break;
 fts5yy_pop_parser_stack(fts5yypParser);
 }
 if( fts5yypParser->fts5yytos <= fts5yypParser->fts5yystack || fts5yymajor==0 ){
 fts5yy_destructor(fts5yypParser,(fts5YYCODETYPE)fts5yymajor,&fts5yyminorunion);
 fts5yy_parse_failed(fts5yypParser);
#ifndef fts5YYNOERRORRECOVERY
 fts5yypParser->fts5yyerrcnt = -1;
#endif
 fts5yymajor = fts5YYNOCODE;
 }else if( fts5yymx!=fts5YYERRORSYMBOL ){
 fts5yy_shift(fts5yypParser,fts5yyact,fts5YYERRORSYMBOL,fts5yyminor);
 }
 }
 fts5yypParser->fts5yyerrcnt = 3;
 fts5yyerrorhit = 1;
 if( fts5yymajor==fts5YYNOCODE ) break;
 fts5yyact = fts5yypParser->fts5yytos->stateno;
#elif defined(fts5YYNOERRORRECOVERY)
 /* If the fts5YYNOERRORRECOVERY macro is defined, then do not attempt to
 ** do any kind of error recovery. Instead, simply invoke the syntax
 ** error routine and continue going as if nothing had happened.
 **
 ** Applications can set this macro (for example inside %include) if
 ** they intend to abandon the parse upon the first syntax error seen.
 */
 fts5yy_syntax_error(fts5yypParser,fts5yymajor, fts5yyminor);
 fts5yy_destructor(fts5yypParser,(fts5YYCODETYPE)fts5yymajor,&fts5yyminorunion);
 break;
#else /* fts5YYERRORSYMBOL is not defined */
 /* This is what we do if the grammar does not define ERROR:
 **
 ** * Report an error message, and throw away the input token.
 **
 ** * If the input token is $, then fail the parse.
 **
 ** As before, subsequent error messages are suppressed until
 ** three input tokens have been successfully shifted.
 */
 if( fts5yypParser->fts5yyerrcnt<=0 ){
 fts5yy_syntax_error(fts5yypParser,fts5yymajor, fts5yyminor);
 }
 fts5yypParser->fts5yyerrcnt = 3;
 fts5yy_destructor(fts5yypParser,(fts5YYCODETYPE)fts5yymajor,&fts5yyminorunion);
 if( fts5yyendofinput ){
 fts5yy_parse_failed(fts5yypParser);
#ifndef fts5YYNOERRORRECOVERY
 fts5yypParser->fts5yyerrcnt = -1;
#endif
 }
 break;
#endif
 }
 }
#ifndef NDEBUG
 if( fts5yyTraceFILE ){
 fts5yyStackEntry *i;
 char cDiv = '[';
 fprintf(fts5yyTraceFILE,"%sReturn. Stack=",fts5yyTracePrompt);
 for(i=&fts5yypParser->fts5yystack[1]; i<=fts5yypParser->fts5yytos; i++){
 fprintf(fts5yyTraceFILE,"%c%s", cDiv, fts5yyTokenName[i->major]);
 cDiv = ' ';
 }
 fprintf(fts5yyTraceFILE,"]\n");
 }
#endif
 return;
}

/*
** Return the fallback token corresponding to canonical token iToken, or
** 0 if iToken has no fallback.
*/
static int sqlite3Fts5ParserFallback(int iToken){
#ifdef fts5YYFALLBACK
 assert( iToken<(int)(sizeof(fts5yyFallback)/sizeof(fts5yyFallback[0])) );
 return fts5yyFallback[iToken];
#else
 (void)iToken;
 return 0;
#endif
}

#line 1 "fts5_aux.c"
/*
** 2014 May 31
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
*/

/* #include "fts5Int.h" */
#include <math.h> /* amalgamator: keep */

/*
** Object used to iterate through all "coalesced phrase instances" in
** a single column of the current row. If the phrase instances in the
** column being considered do not overlap, this object simply iterates
** through them. Or, if they do overlap (share one or more tokens in
** common), each set of overlapping instances is treated as a single
** match. See documentation for the highlight() auxiliary function for
** details.
**
** Usage is:
**
** for(rc = fts5CInstIterNext(pApi, pFts, iCol, &iter);
** (rc==SQLITE_OK && 0==fts5CInstIterEof(&iter);
** rc = fts5CInstIterNext(&iter)
** ){
** printf("instance starts at %d, ends at %d\n", iter.iStart, iter.iEnd);
** }
**
*/
typedef struct CInstIter CInstIter;
struct CInstIter {
 const Fts5ExtensionApi *pApi; /* API offered by current FTS version */
 Fts5Context *pFts; /* First arg to pass to pApi functions */
 int iCol; /* Column to search */
 int iInst; /* Next phrase instance index */
 int nInst; /* Total number of phrase instances */

 /* Output variables */
 int iStart; /* First token in coalesced phrase instance */
 int iEnd; /* Last token in coalesced phrase instance */
};

/*
** Advance the iterator to the next coalesced phrase instance. Return
** an SQLite error code if an error occurs, or SQLITE_OK otherwise.
*/
static int fts5CInstIterNext(CInstIter *pIter){
 int rc = SQLITE_OK;
 pIter->iStart = -1;
 pIter->iEnd = -1;

 while( rc==SQLITE_OK && pIter->iInst<pIter->nInst ){
 int ip; int ic; int io;
 rc = pIter->pApi->xInst(pIter->pFts, pIter->iInst, &ip, &ic, &io);
 if( rc==SQLITE_OK ){
 if( ic==pIter->iCol ){
 int iEnd = io - 1 + pIter->pApi->xPhraseSize(pIter->pFts, ip);
 if( pIter->iStart<0 ){
 pIter->iStart = io;
 pIter->iEnd = iEnd;
 }else if( io<=pIter->iEnd ){
 if( iEnd>pIter->iEnd ) pIter->iEnd = iEnd;
 }else{
 break;
 }
 }
 pIter->iInst++;
 }
 }

 return rc;
}

/*
** Initialize the iterator object indicated by the final parameter to
** iterate through coalesced phrase instances in column iCol.
*/
static int fts5CInstIterInit(
 const Fts5ExtensionApi *pApi,
 Fts5Context *pFts,
 int iCol,
 CInstIter *pIter
){
 int rc;

 memset(pIter, 0, sizeof(CInstIter));
 pIter->pApi = pApi;
 pIter->pFts = pFts;
 pIter->iCol = iCol;
 rc = pApi->xInstCount(pFts, &pIter->nInst);

 if( rc==SQLITE_OK ){
 rc = fts5CInstIterNext(pIter);
 }

 return rc;
}

/*************************************************************************
** Start of highlight() implementation.
*/
typedef struct HighlightContext HighlightContext;
struct HighlightContext {
 /* Constant parameters to fts5HighlightCb() */
 int iRangeStart; /* First token to include */
 int iRangeEnd; /* If non-zero, last token to include */
 const char *zOpen; /* Opening highlight */
 const char *zClose; /* Closing highlight */
 const char *zIn; /* Input text */
 int nIn; /* Size of input text in bytes */

 /* Variables modified by fts5HighlightCb() */
 CInstIter iter; /* Coalesced Instance Iterator */
 int iPos; /* Current token offset in zIn[] */
 int iOff; /* Have copied up to this offset in zIn[] */
 int bOpen; /* True if highlight is open */
 char *zOut; /* Output value */
};

/*
** Append text to the HighlightContext output string - p->zOut. Argument
** z points to a buffer containing n bytes of text to append. If n is
** negative, everything up until the first '\0' is appended to the output.
**
** If *pRc is set to any value other than SQLITE_OK when this function is
** called, it is a no-op. If an error (i.e. an OOM condition) is encountered,
** *pRc is set to an error code before returning.
*/
static void fts5HighlightAppend(
 int *pRc,
 HighlightContext *p,
 const char *z, int n
){
 if( *pRc==SQLITE_OK && z ){
 if( n<0 ) n = (int)strlen(z);
 p->zOut = sqlite3_mprintf("%z%.*s", p->zOut, n, z);
 if( p->zOut==0 ) *pRc = SQLITE_NOMEM;
 }
}

/*
** Tokenizer callback used by implementation of highlight() function.
*/
static int fts5HighlightCb(
 void *pContext, /* Pointer to HighlightContext object */
 int tflags, /* Mask of FTS5_TOKEN_* flags */
 const char *pToken, /* Buffer containing token */
 int nToken, /* Size of token in bytes */
 int iStartOff, /* Start byte offset of token */
 int iEndOff /* End byte offset of token */
){
 HighlightContext *p = (HighlightContext*)pContext;
 int rc = SQLITE_OK;
 int iPos;

 UNUSED_PARAM2(pToken, nToken);

 if( tflags & FTS5_TOKEN_COLOCATED ) return SQLITE_OK;
 iPos = p->iPos++;

 if( p->iRangeEnd>=0 ){
 if( iPos<p->iRangeStart || iPos>p->iRangeEnd ) return SQLITE_OK;
 if( p->iRangeStart && iPos==p->iRangeStart ) p->iOff = iStartOff;
 }

 /* If the parenthesis is open, and this token is not part of the current
 ** phrase, and the starting byte offset of this token is past the point
 ** that has currently been copied into the output buffer, close the
 ** parenthesis. */
 if( p->bOpen
 && (iPos<=p->iter.iStart || p->iter.iStart<0)
 && iStartOff>p->iOff
 ){
 fts5HighlightAppend(&rc, p, p->zClose, -1);
 p->bOpen = 0;
 }

 /* If this is the start of a new phrase, and the highlight is not open:
 **
 ** * copy text from the input up to the start of the phrase, and
 ** * open the highlight.
 */
 if( iPos==p->iter.iStart && p->bOpen==0 ){
 fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iStartOff - p->iOff);
 fts5HighlightAppend(&rc, p, p->zOpen, -1);
 p->iOff = iStartOff;
 p->bOpen = 1;
 }

 if( iPos==p->iter.iEnd ){
 if( p->bOpen==0 ){
 assert( p->iRangeEnd>=0 );
 fts5HighlightAppend(&rc, p, p->zOpen, -1);
 p->bOpen = 1;
 }
 fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iEndOff - p->iOff);
 p->iOff = iEndOff;

 if( rc==SQLITE_OK ){
 rc = fts5CInstIterNext(&p->iter);
 }
 }

 if( iPos==p->iRangeEnd ){
 if( p->bOpen ){
 if( p->iter.iStart>=0 && iPos>=p->iter.iStart ){
 fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iEndOff - p->iOff);
 p->iOff = iEndOff;
 }
 fts5HighlightAppend(&rc, p, p->zClose, -1);
 p->bOpen = 0;
 }
 fts5HighlightAppend(&rc, p, &p->zIn[p->iOff], iEndOff - p->iOff);
 p->iOff = iEndOff;
 }

 return rc;
}

/*
** Implementation of highlight() function.
*/
static void fts5HighlightFunction(
 const Fts5ExtensionApi *pApi, /* API offered by current FTS version */
 Fts5Context *pFts, /* First arg to pass to pApi functions */
 sqlite3_context *pCtx, /* Context for returning result/error */
 int nVal, /* Number of values in apVal[] array */
 sqlite3_value **apVal /* Array of trailing arguments */
){
 HighlightContext ctx;
 int rc;
 int iCol;

 if( nVal!=3 ){
 const char *zErr = "wrong number of arguments to function highlight()";
 sqlite3_result_error(pCtx, zErr, -1);
 return;
 }

 iCol = sqlite3_value_int(apVal[0]);
 memset(&ctx, 0, sizeof(HighlightContext));
 ctx.zOpen = (const char*)sqlite3_value_text(apVal[1]);
 ctx.zClose = (const char*)sqlite3_value_text(apVal[2]);
 ctx.iRangeEnd = -1;
 rc = pApi->xColumnText(pFts, iCol, &ctx.zIn, &ctx.nIn);
 if( rc==SQLITE_RANGE ){
 sqlite3_result_text(pCtx, "", -1, SQLITE_STATIC);
 rc = SQLITE_OK;
 }else if( ctx.zIn ){
 const char *pLoc = 0; /* Locale of column iCol */
 int nLoc = 0; /* Size of pLoc in bytes */
 if( rc==SQLITE_OK ){
 rc = fts5CInstIterInit(pApi, pFts, iCol, &ctx.iter);
 }

 if( rc==SQLITE_OK ){
 rc = pApi->xColumnLocale(pFts, iCol, &pLoc, &nLoc);
 }
 if( rc==SQLITE_OK ){
 rc = pApi->xTokenize_v2(
 pFts, ctx.zIn, ctx.nIn, pLoc, nLoc, (void*)&ctx, fts5HighlightCb
 );
 }
 if( ctx.bOpen ){
 fts5HighlightAppend(&rc, &ctx, ctx.zClose, -1);
 }
 fts5HighlightAppend(&rc, &ctx, &ctx.zIn[ctx.iOff], ctx.nIn - ctx.iOff);

 if( rc==SQLITE_OK ){
 sqlite3_result_text(pCtx, (const char*)ctx.zOut, -1, SQLITE_TRANSIENT);
 }
 sqlite3_free(ctx.zOut);
 }
 if( rc!=SQLITE_OK ){
 sqlite3_result_error_code(pCtx, rc);
 }
}
/*
** End of highlight() implementation.
**************************************************************************/

/*
** Context object passed to the fts5SentenceFinderCb() function.
*/
typedef struct Fts5SFinder Fts5SFinder;
struct Fts5SFinder {
 int iPos; /* Current token position */
 int nFirstAlloc; /* Allocated size of aFirst[] */
 int nFirst; /* Number of entries in aFirst[] */
 int *aFirst; /* Array of first token in each sentence */
 const char *zDoc; /* Document being tokenized */
};

/*
** Add an entry to the Fts5SFinder.aFirst[] array. Grow the array if
** necessary. Return SQLITE_OK if successful, or SQLITE_NOMEM if an
** error occurs.
*/
static int fts5SentenceFinderAdd(Fts5SFinder *p, int iAdd){
 if( p->nFirstAlloc==p->nFirst ){
 int nNew = p->nFirstAlloc ? p->nFirstAlloc*2 : 64;
 int *aNew;

 aNew = (int*)sqlite3_realloc64(p->aFirst, nNew*sizeof(int));
 if( aNew==0 ) return SQLITE_NOMEM;
 p->aFirst = aNew;
 p->nFirstAlloc = nNew;
 }
 p->aFirst[p->nFirst++] = iAdd;
 return SQLITE_OK;
}

/*
** This function is an xTokenize() callback used by the auxiliary snippet()
** function. Its job is to identify tokens that are the first in a sentence.
** For each such token, an entry is added to the SFinder.aFirst[] array.
*/
static int fts5SentenceFinderCb(
 void *pContext, /* Pointer to HighlightContext object */
 int tflags, /* Mask of FTS5_TOKEN_* flags */
 const char *pToken, /* Buffer containing token */
 int nToken, /* Size of token in bytes */
 int iStartOff, /* Start offset of token */
 int iEndOff /* End offset of token */
){
 int rc = SQLITE_OK;

 UNUSED_PARAM2(pToken, nToken);
 UNUSED_PARAM(iEndOff);

 if( (tflags & FTS5_TOKEN_COLOCATED)==0 ){
 Fts5SFinder *p = (Fts5SFinder*)pContext;
 if( p->iPos>0 ){
 int i;
 char c = 0;
 for(i=iStartOff-1; i>=0; i--){
 c = p->zDoc[i];
 if( c!=' ' && c!='\t' && c!='\n' && c!='\r' ) break;
 }
 if( i!=iStartOff-1 && (c=='.' || c==':') ){
 rc = fts5SentenceFinderAdd(p, p->iPos);
 }
 }else{
 rc = fts5SentenceFinderAdd(p, 0);
 }
 p->iPos++;
 }
 return rc;
}

static int fts5SnippetScore(
 const Fts5ExtensionApi *pApi, /* API offered by current FTS version */
 Fts5Context *pFts, /* First arg to pass to pApi functions */
 int nDocsize, /* Size of column in tokens */
 unsigned char *aSeen, /* Array with one element per query phrase */
 int iCol, /* Column to score */
 int iPos, /* Starting offset to score */
 int nToken, /* Max tokens per snippet */
 int *pnScore, /* OUT: Score */
 int *piPos /* OUT: Adjusted offset */
){
 int rc;
 int i;
 int ip = 0;
 int ic = 0;
 int iOff = 0;
 int iFirst = -1;
 int nInst;
 int nScore = 0;
 int iLast = 0;
 sqlite3_int64 iEnd = (sqlite3_int64)iPos + nToken;

 rc = pApi->xInstCount(pFts, &nInst);
 for(i=0; i<nInst && rc==SQLITE_OK; i++){
 rc = pApi->xInst(pFts, i, &ip, &ic, &iOff);
 if( rc==SQLITE_OK && ic==iCol && iOff>=iPos && iOff<iEnd ){
 nScore += (aSeen[ip] ? 1 : 1000);
 aSeen[ip] = 1;
 if( iFirst<0 ) iFirst = iOff;
 iLast = iOff + pApi->xPhraseSize(pFts, ip);
 }
 }

 *pnScore = nScore;
 if( piPos ){
 sqlite3_int64 iAdj = iFirst - (nToken - (iLast-iFirst)) / 2;
 if( (iAdj+nToken)>nDocsize ) iAdj = nDocsize - nToken;
 if( iAdj<0 ) iAdj = 0;
 *piPos = (int)iAdj;
 }

 return rc;
}

/*
** Return the value in pVal interpreted as utf-8 text. Except, if pVal
** contains a NULL value, return a pointer to a static string zero
** bytes in length instead of a NULL pointer.
*/
static const char *fts5ValueToText(sqlite3_value *pVal){
 const char *zRet = (const char*)sqlite3_value_text(pVal);
 return zRet ? zRet : "";
}

/*
** Implementation of snippet() function.
*/
static void fts5SnippetFunction(
 const Fts5ExtensionApi *pApi, /* API offered by current FTS version */
 Fts5Context *pFts, /* First arg to pass to pApi functions */
 sqlite3_context *pCtx, /* Context for returning result/error */
 int nVal, /* Number of values in apVal[] array */
 sqlite3_value **apVal /* Array of trailing arguments */
){
 HighlightContext ctx;
 int rc = SQLITE_OK; /* Return code */
 int iCol; /* 1st argument to snippet() */
 const char *zEllips; /* 4th argument to snippet() */
 int nToken; /* 5th argument to snippet() */
 int nInst = 0; /* Number of instance matches this row */
 int i; /* Used to iterate through instances */
 int nPhrase; /* Number of phrases in query */
 unsigned char *aSeen; /* Array of "seen instance" flags */
 int iBestCol; /* Column containing best snippet */
 int iBestStart = 0; /* First token of best snippet */
 int nBestScore = 0; /* Score of best snippet */
 int nColSize = 0; /* Total size of iBestCol in tokens */
 Fts5SFinder sFinder; /* Used to find the beginnings of sentences */
 int nCol;

 if( nVal!=5 ){
 const char *zErr = "wrong number of arguments to function snippet()";
 sqlite3_result_error(pCtx, zErr, -1);
 return;
 }

 nCol = pApi->xColumnCount(pFts);
 memset(&ctx, 0, sizeof(HighlightContext));
 iCol = sqlite3_value_int(apVal[0]);
 ctx.zOpen = fts5ValueToText(apVal[1]);
 ctx.zClose = fts5ValueToText(apVal[2]);
 ctx.iRangeEnd = -1;
 zEllips = fts5ValueToText(apVal[3]);
 nToken = sqlite3_value_int(apVal[4]);

 iBestCol = (iCol>=0 ? iCol : 0);
 nPhrase = pApi->xPhraseCount(pFts);
 aSeen = sqlite3_malloc(nPhrase);
 if( aSeen==0 ){
 rc = SQLITE_NOMEM;
 }
 if( rc==SQLITE_OK ){
 rc = pApi->xInstCount(pFts, &nInst);
 }

 memset(&sFinder, 0, sizeof(Fts5SFinder));
 for(i=0; i<nCol; i++){
 if( iCol<0 || iCol==i ){
 const char *pLoc = 0; /* Locale of column iCol */
 int nLoc = 0; /* Size of pLoc in bytes */
 int nDoc;
 int nDocsize;
 int ii;
 sFinder.iPos = 0;
 sFinder.nFirst = 0;
 rc = pApi->xColumnText(pFts, i, &sFinder.zDoc, &nDoc);
 if( rc!=SQLITE_OK ) break;
 rc = pApi->xColumnLocale(pFts, i, &pLoc, &nLoc);
 if( rc!=SQLITE_OK ) break;
 rc = pApi->xTokenize_v2(pFts,
 sFinder.zDoc, nDoc, pLoc, nLoc, (void*)&sFinder, fts5SentenceFinderCb
 );
 if( rc!=SQLITE_OK ) break;
 rc = pApi->xColumnSize(pFts, i, &nDocsize);
 if( rc!=SQLITE_OK ) break;

 for(ii=0; rc==SQLITE_OK && ii<nInst; ii++){
 int ip, ic, io;
 int iAdj;
 int nScore;
 int jj;

 rc = pApi->xInst(pFts, ii, &ip, &ic, &io);
 if( ic!=i ) continue;
 if( io>nDocsize ) rc = FTS5_CORRUPT;
 if( rc!=SQLITE_OK ) continue;
 memset(aSeen, 0, nPhrase);
 rc = fts5SnippetScore(pApi, pFts, nDocsize, aSeen, i,
 io, nToken, &nScore, &iAdj
 );
 if( rc==SQLITE_OK && nScore>nBestScore ){
 nBestScore = nScore;
 iBestCol = i;
 iBestStart = iAdj;
 nColSize = nDocsize;
 }

 if( rc==SQLITE_OK && sFinder.nFirst && nDocsize>nToken ){
 for(jj=0; jj<(sFinder.nFirst-1); jj++){
 if( sFinder.aFirst[jj+1]>io ) break;
 }

 if( sFinder.aFirst[jj]<io ){
 memset(aSeen, 0, nPhrase);
 rc = fts5SnippetScore(pApi, pFts, nDocsize, aSeen, i,
 sFinder.aFirst[jj], nToken, &nScore, 0
 );

 nScore += (sFinder.aFirst[jj]==0 ? 120 : 100);
 if( rc==SQLITE_OK && nScore>nBestScore ){
 nBestScore = nScore;
 iBestCol = i;
 iBestStart = sFinder.aFirst[jj];
 nColSize = nDocsize;
 }
 }
 }
 }
 }
 }

 if( rc==SQLITE_OK ){
 rc = pApi->xColumnText(pFts, iBestCol, &ctx.zIn, &ctx.nIn);
 }
 if( rc==SQLITE_OK && nColSize==0 ){
 rc = pApi->xColumnSize(pFts, iBestCol, &nColSize);
 }
 if( ctx.zIn ){
 const char *pLoc = 0; /* Locale of column iBestCol */
 int nLoc = 0; /* Bytes in pLoc */

 if( rc==SQLITE_OK ){
 rc = fts5CInstIterInit(pApi, pFts, iBestCol, &ctx.iter);
 }

 ctx.iRangeStart = iBestStart;
 ctx.iRangeEnd = iBestStart + nToken - 1;

 if( iBestStart>0 ){
 fts5HighlightAppend(&rc, &ctx, zEllips, -1);
 }

 /* Advance iterator ctx.iter so that it points to the first coalesced
 ** phrase instance at or following position iBestStart. */
 while( ctx.iter.iStart>=0 && ctx.iter.iStart<iBestStart && rc==SQLITE_OK ){
 rc = fts5CInstIterNext(&ctx.iter);
 }

 if( rc==SQLITE_OK ){
 rc = pApi->xColumnLocale(pFts, iBestCol, &pLoc, &nLoc);
 }
 if( rc==SQLITE_OK ){
 rc = pApi->xTokenize_v2(
 pFts, ctx.zIn, ctx.nIn, pLoc, nLoc, (void*)&ctx,fts5HighlightCb
 );
 }
 if( ctx.bOpen ){
 fts5HighlightAppend(&rc, &ctx, ctx.zClose, -1);
 }
 if( ctx.iRangeEnd>=(nColSize-1) ){
 fts5HighlightAppend(&rc, &ctx, &ctx.zIn[ctx.iOff], ctx.nIn - ctx.iOff);
 }else{
 fts5HighlightAppend(&rc, &ctx, zEllips, -1);
 }
 }
 if( rc==SQLITE_OK ){
 sqlite3_result_text(pCtx, (const char*)ctx.zOut, -1, SQLITE_TRANSIENT);
 }else{
 sqlite3_result_error_code(pCtx, rc);
 }
 sqlite3_free(ctx.zOut);
 sqlite3_free(aSeen);
 sqlite3_free(sFinder.aFirst);
}

/************************************************************************/

/*
** The first time the bm25() function is called for a query, an instance
** of the following structure is allocated and populated.
*/
typedef struct Fts5Bm25Data Fts5Bm25Data;
struct Fts5Bm25Data {
 int nPhrase; /* Number of phrases in query */
 double avgdl; /* Average number of tokens in each row */
 double *aIDF; /* IDF for each phrase */
 double *aFreq; /* Array used to calculate phrase freq. */
};

/*
** Callback used by fts5Bm25GetData() to count the number of rows in the
** table matched by each individual phrase within the query.
*/
static int fts5CountCb(
 const Fts5ExtensionApi *pApi,
 Fts5Context *pFts,
 void *pUserData /* Pointer to sqlite3_int64 variable */
){
 sqlite3_int64 *pn = (sqlite3_int64*)pUserData;
 UNUSED_PARAM2(pApi, pFts);
 (*pn)++;
 return SQLITE_OK;
}

/*
** Set *ppData to point to the Fts5Bm25Data object for the current query.
** If the object has not already been allocated, allocate and populate it
** now.
*/
static int fts5Bm25GetData(
 const Fts5ExtensionApi *pApi,
 Fts5Context *pFts,
 Fts5Bm25Data **ppData /* OUT: bm25-data object for this query */
){
 int rc = SQLITE_OK; /* Return code */
 Fts5Bm25Data *p; /* Object to return */

 p = (Fts5Bm25Data*)pApi->xGetAuxdata(pFts, 0);
 if( p==0 ){
 int nPhrase; /* Number of phrases in query */
 sqlite3_int64 nRow = 0; /* Number of rows in table */
 sqlite3_int64 nToken = 0; /* Number of tokens in table */
 sqlite3_int64 nByte; /* Bytes of space to allocate */
 int i;

 /* Allocate the Fts5Bm25Data object */
 nPhrase = pApi->xPhraseCount(pFts);
 nByte = sizeof(Fts5Bm25Data) + nPhrase*2*sizeof(double);
 p = (Fts5Bm25Data*)sqlite3_malloc64(nByte);
 if( p==0 ){
 rc = SQLITE_NOMEM;
 }else{
 memset(p, 0, (size_t)nByte);
 p->nPhrase = nPhrase;
 p->aIDF = (double*)&p[1];
 p->aFreq = &p->aIDF[nPhrase];
 }

 /* Calculate the average document length for this FTS5 table */
 if( rc==SQLITE_OK ) rc = pApi->xRowCount(pFts, &nRow);
 assert( rc!=SQLITE_OK || nRow>0 );
 if( rc==SQLITE_OK ) rc = pApi->xColumnTotalSize(pFts, -1, &nToken);
 if( rc==SQLITE_OK ) p->avgdl = (double)nToken / (double)nRow;

 /* Calculate an IDF for each phrase in the query */
 for(i=0; rc==SQLITE_OK && i<nPhrase; i++){
 sqlite3_int64 nHit = 0;
 rc = pApi->xQueryPhrase(pFts, i, (void*)&nHit, fts5CountCb);
 if( rc==SQLITE_OK ){
 /* Calculate the IDF (Inverse Document Frequency) for phrase i.
 ** This is done using the standard BM25 formula as found on wikipedia:
 **
 ** IDF = log( (N - nHit + 0.5) / (nHit + 0.5) )
 **
 ** where "N" is the total number of documents in the set and nHit
 ** is the number that contain at least one instance of the phrase
 ** under consideration.
 **
 ** The problem with this is that if (N < 2*nHit), the IDF is
 ** negative. Which is undesirable. So the mimimum allowable IDF is
 ** (1e-6) - roughly the same as a term that appears in just over
 ** half of set of 5,000,000 documents. */
 double idf = log( (nRow - nHit + 0.5) / (nHit + 0.5) );
 if( idf<=0.0 ) idf = 1e-6;
 p->aIDF[i] = idf;
 }
 }

 if( rc!=SQLITE_OK ){
 sqlite3_free(p);
 }else{
 rc = pApi->xSetAuxdata(pFts, p, sqlite3_free);
 }
 if( rc!=SQLITE_OK ) p = 0;
 }
 *ppData = p;
 return rc;
}

/*
** Implementation of bm25() function.
*/
static void fts5Bm25Function(
 const Fts5ExtensionApi *pApi, /* API offered by current FTS version */
 Fts5Context *pFts, /* First arg to pass to pApi functions */
 sqlite3_context *pCtx, /* Context for returning result/error */
 int nVal, /* Number of values in apVal[] array */
 sqlite3_value **apVal /* Array of trailing arguments */
){
 const double k1 = 1.2; /* Constant "k1" from BM25 formula */
 const double b = 0.75; /* Constant "b" from BM25 formula */
 int rc; /* Error code */
 double score = 0.0; /* SQL function return value */
 Fts5Bm25Data *pData; /* Values allocated/calculated once only */
 int i; /* Iterator variable */
 int nInst = 0; /* Value returned by xInstCount() */
 double D = 0.0; /* Total number of tokens in row */
 double *aFreq = 0; /* Array of phrase freq. for current row */

 /* Calculate the phrase frequency (symbol "f(qi,D)" in the documentation)
 ** for each phrase in the query for the current row. */
 rc = fts5Bm25GetData(pApi, pFts, &pData);
 if( rc==SQLITE_OK ){
 aFreq = pData->aFreq;
 memset(aFreq, 0, sizeof(double) * pData->nPhrase);
 rc = pApi->xInstCount(pFts, &nInst);
 }
 for(i=0; rc==SQLITE_OK && i<nInst; i++){
 int ip; int ic; int io;
 rc = pApi->xInst(pFts, i, &ip, &ic, &io);
 if( rc==SQLITE_OK ){
 double w = (nVal > ic) ? sqlite3_value_double(apVal[ic]) : 1.0;
 aFreq[ip] += w;
 }
 }

 /* Figure out the total size of the current row in tokens. */
 if( rc==SQLITE_OK ){
 int nTok;
 rc = pApi->xColumnSize(pFts, -1, &nTok);
 D = (double)nTok;
 }

 /* Determine and return the BM25 score for the current row. Or, if an
 ** error has occurred, throw an exception. */
 if( rc==SQLITE_OK ){
 for(i=0; i<pData->nPhrase; i++){
 score += pData->aIDF[i] * (
 ( aFreq[i] * (k1 + 1.0) ) /
 ( aFreq[i] + k1 * (1 - b + b * D / pData->avgdl) )
 );
 }
 sqlite3_result_double(pCtx, -1.0 * score);
 }else{
 sqlite3_result_error_code(pCtx, rc);
 }
}

/*
** Implementation of fts5_get_locale() function.
*/
static void fts5GetLocaleFunction(
 const Fts5ExtensionApi *pApi, /* API offered by current FTS version */
 Fts5Context *pFts, /* First arg to pass to pApi functions */
 sqlite3_context *pCtx, /* Context for returning result/error */
 int nVal, /* Number of values in apVal[] array */
 sqlite3_value **apVal /* Array of trailing arguments */
){
 int iCol = 0;
 int eType = 0;
 int rc = SQLITE_OK;
 const char *zLocale = 0;
 int nLocale = 0;

 /* xColumnLocale() must be available */
 assert( pApi->iVersion>=4 );

 if( nVal!=1 ){
 const char *z = "wrong number of arguments to function fts5_get_locale()";
 sqlite3_result_error(pCtx, z, -1);
 return;
 }

 eType = sqlite3_value_numeric_type(apVal[0]);
 if( eType!=SQLITE_INTEGER ){
 const char *z = "non-integer argument passed to function fts5_get_locale()";
 sqlite3_result_error(pCtx, z, -1);
 return;
 }

 iCol = sqlite3_value_int(apVal[0]);
 if( iCol<0 || iCol>=pApi->xColumnCount(pFts) ){
 sqlite3_result_error_code(pCtx, SQLITE_RANGE);
 return;
 }

 rc = pApi->xColumnLocale(pFts, iCol, &zLocale, &nLocale);
 if( rc!=SQLITE_OK ){
 sqlite3_result_error_code(pCtx, rc);
 return;
 }

 sqlite3_result_text(pCtx, zLocale, nLocale, SQLITE_TRANSIENT);
}

static int sqlite3Fts5AuxInit(fts5_api *pApi){
 struct Builtin {
 const char *zFunc; /* Function name (nul-terminated) */
 void *pUserData; /* User-data pointer */
 fts5_extension_function xFunc;/* Callback function */
 void (*xDestroy)(void*); /* Destructor function */
 } aBuiltin [] = {
 { "snippet", 0, fts5SnippetFunction, 0 },
 { "highlight", 0, fts5HighlightFunction, 0 },
 { "bm25", 0, fts5Bm25Function, 0 },
 { "fts5_get_locale", 0, fts5GetLocaleFunction, 0 },
 };
 int rc = SQLITE_OK; /* Return code */
 int i; /* To iterate through builtin functions */

 for(i=0; rc==SQLITE_OK && i<ArraySize(aBuiltin); i++){
 rc = pApi->xCreateFunction(pApi,
 aBuiltin[i].zFunc,
 aBuiltin[i].pUserData,
 aBuiltin[i].xFunc,
 aBuiltin[i].xDestroy
 );
 }

 return rc;
}

#line 1 "fts5_buffer.c"
/*
** 2014 May 31
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
*/

/* #include "fts5Int.h" */

static int sqlite3Fts5BufferSize(int *pRc, Fts5Buffer *pBuf, u32 nByte){
 if( (u32)pBuf->nSpace<nByte ){
 u64 nNew = pBuf->nSpace ? pBuf->nSpace : 64;
 u8 *pNew;
 while( nNew<nByte ){
 nNew = nNew * 2;
 }
 pNew = sqlite3_realloc64(pBuf->p, nNew);
 if( pNew==0 ){
 *pRc = SQLITE_NOMEM;
 return 1;
 }else{
 pBuf->nSpace = (int)nNew;
 pBuf->p = pNew;
 }
 }
 return 0;
}

/*
** Encode value iVal as an SQLite varint and append it to the buffer object
** pBuf. If an OOM error occurs, set the error code in p.
*/
static void sqlite3Fts5BufferAppendVarint(int *pRc, Fts5Buffer *pBuf, i64 iVal){
 if( fts5BufferGrow(pRc, pBuf, 9) ) return;
 pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iVal);
}

static void sqlite3Fts5Put32(u8 *aBuf, int iVal){
 aBuf[0] = (iVal>>24) & 0x00FF;
 aBuf[1] = (iVal>>16) & 0x00FF;
 aBuf[2] = (iVal>> 8) & 0x00FF;
 aBuf[3] = (iVal>> 0) & 0x00FF;
}

static int sqlite3Fts5Get32(const u8 *aBuf){
 return (int)((((u32)aBuf[0])<<24) + (aBuf[1]<<16) + (aBuf[2]<<8) + aBuf[3]);
}

/*
** Append buffer nData/pData to buffer pBuf. If an OOM error occurs, set
** the error code in p. If an error has already occurred when this function
** is called, it is a no-op.
*/
static void sqlite3Fts5BufferAppendBlob(
 int *pRc,
 Fts5Buffer *pBuf,
 u32 nData,
 const u8 *pData
){
 if( nData ){
 if( fts5BufferGrow(pRc, pBuf, nData) ) return;
 assert( pBuf->p!=0 );
 memcpy(&pBuf->p[pBuf->n], pData, nData);
 pBuf->n += nData;
 }
}

/*
** Append the nul-terminated string zStr to the buffer pBuf. This function
** ensures that the byte following the buffer data is set to 0x00, even
** though this byte is not included in the pBuf->n count.
*/
static void sqlite3Fts5BufferAppendString(
 int *pRc,
 Fts5Buffer *pBuf,
 const char *zStr
){
 int nStr = (int)strlen(zStr);
 sqlite3Fts5BufferAppendBlob(pRc, pBuf, nStr+1, (const u8*)zStr);
 pBuf->n--;
}

/*
** Argument zFmt is a printf() style format string. This function performs
** the printf() style processing, then appends the results to buffer pBuf.
**
** Like sqlite3Fts5BufferAppendString(), this function ensures that the byte
** following the buffer data is set to 0x00, even though this byte is not
** included in the pBuf->n count.
*/
static void sqlite3Fts5BufferAppendPrintf(
 int *pRc,
 Fts5Buffer *pBuf,
 char *zFmt, ...
){
 if( *pRc==SQLITE_OK ){
 char *zTmp;
 va_list ap;
 va_start(ap, zFmt);
 zTmp = sqlite3_vmprintf(zFmt, ap);
 va_end(ap);

 if( zTmp==0 ){
 *pRc = SQLITE_NOMEM;
 }else{
 sqlite3Fts5BufferAppendString(pRc, pBuf, zTmp);
 sqlite3_free(zTmp);
 }
 }
}

static char *sqlite3Fts5Mprintf(int *pRc, const char *zFmt, ...){
 char *zRet = 0;
 if( *pRc==SQLITE_OK ){
 va_list ap;
 va_start(ap, zFmt);
 zRet = sqlite3_vmprintf(zFmt, ap);
 va_end(ap);
 if( zRet==0 ){
 *pRc = SQLITE_NOMEM;
 }
 }
 return zRet;
}

/*
** Free any buffer allocated by pBuf. Zero the structure before returning.
*/
static void sqlite3Fts5BufferFree(Fts5Buffer *pBuf){
 sqlite3_free(pBuf->p);
 memset(pBuf, 0, sizeof(Fts5Buffer));
}

/*
** Zero the contents of the buffer object. But do not free the associated
** memory allocation.
*/
static void sqlite3Fts5BufferZero(Fts5Buffer *pBuf){
 pBuf->n = 0;
}

/*
** Set the buffer to contain nData/pData. If an OOM error occurs, leave an
** the error code in p. If an error has already occurred when this function
** is called, it is a no-op.
*/
static void sqlite3Fts5BufferSet(
 int *pRc,
 Fts5Buffer *pBuf,
 int nData,
 const u8 *pData
){
 pBuf->n = 0;
 sqlite3Fts5BufferAppendBlob(pRc, pBuf, nData, pData);
}

static int sqlite3Fts5PoslistNext64(
 const u8 *a, int n, /* Buffer containing poslist */
 int *pi, /* IN/OUT: Offset within a[] */
 i64 *piOff /* IN/OUT: Current offset */
){
 int i = *pi;
 assert( a!=0 || i==0 );
 if( i>=n ){
 /* EOF */
 *piOff = -1;
 return 1;
 }else{
 i64 iOff = *piOff;
 u32 iVal;
 assert( a!=0 );
 fts5FastGetVarint32(a, i, iVal);
 if( iVal<=1 ){
 if( iVal==0 ){
 *pi = i;
 return 0;
 }
 fts5FastGetVarint32(a, i, iVal);
 iOff = ((i64)iVal) << 32;
 assert( iOff>=0 );
 fts5FastGetVarint32(a, i, iVal);
 if( iVal<2 ){
 /* This is a corrupt record. So stop parsing it here. */
 *piOff = -1;
 return 1;
 }
 *piOff = iOff + ((iVal-2) & 0x7FFFFFFF);
 }else{
 *piOff = (iOff & (i64)0x7FFFFFFF<<32)+((iOff + (iVal-2)) & 0x7FFFFFFF);
 }
 *pi = i;
 assert_nc( *piOff>=iOff );
 return 0;
 }
}

/*
** Advance the iterator object passed as the only argument. Return true
** if the iterator reaches EOF, or false otherwise.
*/
static int sqlite3Fts5PoslistReaderNext(Fts5PoslistReader *pIter){
 if( sqlite3Fts5PoslistNext64(pIter->a, pIter->n, &pIter->i, &pIter->iPos) ){
 pIter->bEof = 1;
 }
 return pIter->bEof;
}

static int sqlite3Fts5PoslistReaderInit(
 const u8 *a, int n, /* Poslist buffer to iterate through */
 Fts5PoslistReader *pIter /* Iterator object to initialize */
){
 memset(pIter, 0, sizeof(*pIter));
 pIter->a = a;
 pIter->n = n;
 sqlite3Fts5PoslistReaderNext(pIter);
 return pIter->bEof;
}

/*
** Append position iPos to the position list being accumulated in buffer
** pBuf, which must be already be large enough to hold the new data.
** The previous position written to this list is *piPrev. *piPrev is set
** to iPos before returning.
*/
static void sqlite3Fts5PoslistSafeAppend(
 Fts5Buffer *pBuf,
 i64 *piPrev,
 i64 iPos
){
 if( iPos>=*piPrev ){
 static const i64 colmask = ((i64)(0x7FFFFFFF)) << 32;
 if( (iPos & colmask) != (*piPrev & colmask) ){
 pBuf->p[pBuf->n++] = 1;
 pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], (iPos>>32));
 *piPrev = (iPos & colmask);
 }
 pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], (iPos-*piPrev)+2);
 *piPrev = iPos;
 }
}

static int sqlite3Fts5PoslistWriterAppend(
 Fts5Buffer *pBuf,
 Fts5PoslistWriter *pWriter,
 i64 iPos
){
 int rc = 0; /* Initialized only to suppress erroneous warning from Clang */
 if( fts5BufferGrow(&rc, pBuf, 5+5+5) ) return rc;
 sqlite3Fts5PoslistSafeAppend(pBuf, &pWriter->iPrev, iPos);
 return SQLITE_OK;
}

static void *sqlite3Fts5MallocZero(int *pRc, sqlite3_int64 nByte){
 void *pRet = 0;
 if( *pRc==SQLITE_OK ){
 pRet = sqlite3_malloc64(nByte);
 if( pRet==0 ){
 if( nByte>0 ) *pRc = SQLITE_NOMEM;
 }else{
 memset(pRet, 0, (size_t)nByte);
 }
 }
 return pRet;
}

/*
** Return a nul-terminated copy of the string indicated by pIn. If nIn
** is non-negative, then it is the length of the string in bytes. Otherwise,
** the length of the string is determined using strlen().
**
** It is the responsibility of the caller to eventually free the returned
** buffer using sqlite3_free(). If an OOM error occurs, NULL is returned.
*/
static char *sqlite3Fts5Strndup(int *pRc, const char *pIn, int nIn){
 char *zRet = 0;
 if( *pRc==SQLITE_OK ){
 if( nIn<0 ){
 nIn = (int)strlen(pIn);
 }
 zRet = (char*)sqlite3_malloc(nIn+1);
 if( zRet ){
 memcpy(zRet, pIn, nIn);
 zRet[nIn] = '\0';
 }else{
 *pRc = SQLITE_NOMEM;
 }
 }
 return zRet;
}

/*
** Return true if character 't' may be part of an FTS5 bareword, or false
** otherwise. Characters that may be part of barewords:
**
** * All non-ASCII characters,
** * The 52 upper and lower case ASCII characters, and
** * The 10 integer ASCII characters.
** * The underscore character "_" (0x5F).
** * The unicode "subsitute" character (0x1A).
*/
static int sqlite3Fts5IsBareword(char t){
 u8 aBareword[128] = {
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0x00 .. 0x0F */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, /* 0x10 .. 0x1F */
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* 0x20 .. 0x2F */
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, /* 0x30 .. 0x3F */
 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x40 .. 0x4F */
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, /* 0x50 .. 0x5F */
 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 0x60 .. 0x6F */
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 /* 0x70 .. 0x7F */
 };

 return (t & 0x80) || aBareword[(int)t];
}

/*************************************************************************
*/
typedef struct Fts5TermsetEntry Fts5TermsetEntry;
struct Fts5TermsetEntry {
 char *pTerm;
 int nTerm;
 int iIdx; /* Index (main or aPrefix[] entry) */
 Fts5TermsetEntry *pNext;
};

struct Fts5Termset {
 Fts5TermsetEntry *apHash[512];
};

static int sqlite3Fts5TermsetNew(Fts5Termset **pp){
 int rc = SQLITE_OK;
 *pp = sqlite3Fts5MallocZero(&rc, sizeof(Fts5Termset));
 return rc;
}

static int sqlite3Fts5TermsetAdd(
 Fts5Termset *p,
 int iIdx,
 const char *pTerm, int nTerm,
 int *pbPresent
){
 int rc = SQLITE_OK;
 *pbPresent = 0;
 if( p ){
 int i;
 u32 hash = 13;
 Fts5TermsetEntry *pEntry;

 /* Calculate a hash value for this term. This is the same hash checksum
 ** used by the fts5_hash.c module. This is not important for correct
 ** operation of the module, but is necessary to ensure that some tests
 ** designed to produce hash table collisions really do work. */
 for(i=nTerm-1; i>=0; i--){
 hash = (hash << 3) ^ hash ^ pTerm[i];
 }
 hash = (hash << 3) ^ hash ^ iIdx;
 hash = hash % ArraySize(p->apHash);

 for(pEntry=p->apHash[hash]; pEntry; pEntry=pEntry->pNext){
 if( pEntry->iIdx==iIdx
 && pEntry->nTerm==nTerm
 && memcmp(pEntry->pTerm, pTerm, nTerm)==0
 ){
 *pbPresent = 1;
 break;
 }
 }

 if( pEntry==0 ){
 pEntry = sqlite3Fts5MallocZero(&rc, sizeof(Fts5TermsetEntry) + nTerm);
 if( pEntry ){
 pEntry->pTerm = (char*)&pEntry[1];
 pEntry->nTerm = nTerm;
 pEntry->iIdx = iIdx;
 memcpy(pEntry->pTerm, pTerm, nTerm);
 pEntry->pNext = p->apHash[hash];
 p->apHash[hash] = pEntry;
 }
 }
 }

 return rc;
}

static void sqlite3Fts5TermsetFree(Fts5Termset *p){
 if( p ){
 u32 i;
 for(i=0; i<ArraySize(p->apHash); i++){
 Fts5TermsetEntry *pEntry = p->apHash[i];
 while( pEntry ){
 Fts5TermsetEntry *pDel = pEntry;
 pEntry = pEntry->pNext;
 sqlite3_free(pDel);
 }
 }
 sqlite3_free(p);
 }
}

#line 1 "fts5_config.c"
/*
** 2014 Jun 09
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This is an SQLite module implementing full-text search.
*/

/* #include "fts5Int.h" */

#define FTS5_DEFAULT_PAGE_SIZE 4050
#define FTS5_DEFAULT_AUTOMERGE 4
#define FTS5_DEFAULT_USERMERGE 4
#define FTS5_DEFAULT_CRISISMERGE 16
#define FTS5_DEFAULT_HASHSIZE (1024*1024)

#define FTS5_DEFAULT_DELETE_AUTOMERGE 10 /* default 10% */

/* Maximum allowed page size */
#define FTS5_MAX_PAGE_SIZE (64*1024)

static int fts5_iswhitespace(char x){
 return (x==' ');
}

static int fts5_isopenquote(char x){
 return (x=='"' || x=='\'' || x=='[' || x=='`');
}

/*
** Argument pIn points to a character that is part of a nul-terminated
** string. Return a pointer to the first character following *pIn in
** the string that is not a white-space character.
*/
static const char *fts5ConfigSkipWhitespace(const char *pIn){
 const char *p = pIn;
 if( p ){
 while( fts5_iswhitespace(*p) ){ p++; }
 }
 return p;
}

/*
** Argument pIn points to a character that is part of a nul-terminated
** string. Return a pointer to the first character following *pIn in
** the string that is not a "bareword" character.
*/
static const char *fts5ConfigSkipBareword(const char *pIn){
 const char *p = pIn;
 while ( sqlite3Fts5IsBareword(*p) ) p++;
 if( p==pIn ) p = 0;
 return p;
}

static int fts5_isdigit(char a){
 return (a>='0' && a<='9');
}

static const char *fts5ConfigSkipLiteral(const char *pIn){
 const char *p = pIn;
 switch( *p ){
 case 'n': case 'N':
 if( sqlite3_strnicmp("null", p, 4)==0 ){
 p = &p[4];
 }else{
 p = 0;
 }
 break;

 case 'x': case 'X':
 p++;
 if( *p=='\'' ){
 p++;
 while( (*p>='a' && *p<='f')
 || (*p>='A' && *p<='F')
 || (*p>='0' && *p<='9')
 ){
 p++;
 }
 if( *p=='\'' && 0==((p-pIn)%2) ){
 p++;
 }else{
 p = 0;
 }
 }else{
 p = 0;
 }
 break;

 case '\'':
 p++;
 while( p ){
 if( *p=='\'' ){
 p++;
 if( *p!='\'' ) break;
 }
 p++;
 if( *p==0 ) p = 0;
 }
 break;

 default:
 /* maybe a number */
 if( *p=='+' || *p=='-' ) p++;
 while( fts5_isdigit(*p) ) p++;

 /* At this point, if the literal was an integer, the parse is
 ** finished. Or, if it is a floating point value, it may continue
 ** with either a decimal point or an 'E' character. */
 if( *p=='.' && fts5_isdigit(p[1]) ){
 p += 2;
 while( fts5_isdigit(*p) ) p++;
 }
 if( p==pIn ) p = 0;

 break;
 }

 return p;
}

/*
** The first character of the string pointed to by argument z is guaranteed
** to be an open-quote character (see function fts5_isopenquote()).
**
** This function searches for the corresponding close-quote character within
** the string and, if found, dequotes the string in place and adds a new
** nul-terminator byte.
**
** If the close-quote is found, the value returned is the byte offset of
** the character immediately following it. Or, if the close-quote is not
** found, -1 is returned. If -1 is returned, the buffer is left in an
** undefined state.
*/
static int fts5Dequote(char *z){
 char q;
 int iIn = 1;
 int iOut = 0;
 q = z[0];

 /* Set stack variable q to the close-quote character */
 assert( q=='[' || q=='\'' || q=='"' || q=='`' );
 if( q=='[' ) q = ']';

 while( z[iIn] ){
 if( z[iIn]==q ){
 if( z[iIn+1]!=q ){
 /* Character iIn was the close quote. */
 iIn++;
 break;
 }else{
 /* Character iIn and iIn+1 form an escaped quote character. Skip
 ** the input cursor past both and copy a single quote character
 ** to the output buffer. */
 iIn += 2;
 z[iOut++] = q;
 }
 }else{
 z[iOut++] = z[iIn++];
 }
 }

 z[iOut] = '\0';
 return iIn;
}

/*
** Convert an SQL-style quoted string into a normal string by removing
** the quote characters. The conversion is done in-place. If the
** input does not begin with a quote character, then this routine
** is a no-op.
**
** Examples:
**
** "abc" becomes abc
** 'xyz' becomes xyz
** [pqr] becomes pqr
** `mno` becomes mno
*/
static void sqlite3Fts5Dequote(char *z){
 char quote; /* Quote character (if any ) */

 assert( 0==fts5_iswhitespace(z[0]) );
 quote = z[0];
 if( quote=='[' || quote=='\'' || quote=='"' || quote=='`' ){
 fts5Dequote(z);
 }
}

struct Fts5Enum {
 const char *zName;
 int eVal;
};
typedef struct Fts5Enum Fts5Enum;

static int fts5ConfigSetEnum(
 const Fts5Enum *aEnum,
 const char *zEnum,
 int *peVal
){
 int nEnum = (int)strlen(zEnum);
 int i;
 int iVal = -1;

 for(i=0; aEnum[i].zName; i++){
 if( sqlite3_strnicmp(aEnum[i].zName, zEnum, nEnum)==0 ){
 if( iVal>=0 ) return SQLITE_ERROR;
 iVal = aEnum[i].eVal;
 }
 }

 *peVal = iVal;
 return iVal<0 ? SQLITE_ERROR : SQLITE_OK;
}

/*
** Parse a "special" CREATE VIRTUAL TABLE directive and update
** configuration object pConfig as appropriate.
**
** If successful, object pConfig is updated and SQLITE_OK returned. If
** an error occurs, an SQLite error code is returned and an error message
** may be left in *pzErr. It is the responsibility of the caller to
** eventually free any such error message using sqlite3_free().
*/
static int fts5ConfigParseSpecial(
 Fts5Config *pConfig, /* Configuration object to update */
 const char *zCmd, /* Special command to parse */
 const char *zArg, /* Argument to parse */
 char **pzErr /* OUT: Error message */
){
 int rc = SQLITE_OK;
 int nCmd = (int)strlen(zCmd);

 if( sqlite3_strnicmp("prefix", zCmd, nCmd)==0 ){
 const int nByte = sizeof(int) * FTS5_MAX_PREFIX_INDEXES;
 const char *p;
 int bFirst = 1;
 if( pConfig->aPrefix==0 ){
 pConfig->aPrefix = sqlite3Fts5MallocZero(&rc, nByte);
 if( rc ) return rc;
 }

 p = zArg;
 while( 1 ){
 int nPre = 0;

 while( p[0]==' ' ) p++;
 if( bFirst==0 && p[0]==',' ){
 p++;
 while( p[0]==' ' ) p++;
 }else if( p[0]=='\0' ){
 break;
 }
 if( p[0]<'0' || p[0]>'9' ){
 *pzErr = sqlite3_mprintf("malformed prefix=... directive");
 rc = SQLITE_ERROR;
 break;
 }

 if( pConfig->nPrefix==FTS5_MAX_PREFIX_INDEXES ){
 *pzErr = sqlite3_mprintf(
 "too many prefix indexes (max %d)", FTS5_MAX_PREFIX_INDEXES
 );
 rc = SQLITE_ERROR;
 break;
 }

 while( p[0]>='0' && p[0]<='9' && nPre<1000 ){
 nPre = nPre*10 + (p[0] - '0');
 p++;
 }

 if( nPre<=0 || nPre>=1000 ){
 *pzErr = sqlite3_mprintf("prefix length out of range (max 999)");
 rc = SQLITE_ERROR;
 break;
 }

 pConfig->aPrefix[pConfig->nPrefix] = nPre;
 pConfig->nPrefix++;
 bFirst = 0;
 }
 assert( pConfig->nPrefix<=FTS5_MAX_PREFIX_INDEXES );
 return rc;
 }

 if( sqlite3_strnicmp("tokenize", zCmd, nCmd)==0 ){
 const char *p = (const char*)zArg;
 sqlite3_int64 nArg = strlen(zArg) + 1;
 char **azArg = sqlite3Fts5MallocZero(&rc, (sizeof(char*) + 2) * nArg);

 if( azArg ){
 char *pSpace = (char*)&azArg[nArg];
 if( pConfig->t.azArg ){
 *pzErr = sqlite3_mprintf("multiple tokenize=... directives");
 rc = SQLITE_ERROR;
 }else{
 for(nArg=0; p && *p; nArg++){
 const char *p2 = fts5ConfigSkipWhitespace(p);
 if( *p2=='\'' ){
 p = fts5ConfigSkipLiteral(p2);
 }else{
 p = fts5ConfigSkipBareword(p2);
 }
 if( p ){
 memcpy(pSpace, p2, p-p2);
 azArg[nArg] = pSpace;
 sqlite3Fts5Dequote(pSpace);
 pSpace += (p - p2) + 1;
 p = fts5ConfigSkipWhitespace(p);
 }
 }
 if( p==0 ){
 *pzErr = sqlite3_mprintf("parse error in tokenize directive");
 rc = SQLITE_ERROR;
 }else{
 pConfig->t.azArg = (const char**)azArg;
 pConfig->t.nArg = nArg;
 azArg = 0;
 }
 }
 }
 sqlite3_free(azArg);

 return rc;
 }

 if( sqlite3_strnicmp("content", zCmd, nCmd)==0 ){
 if( pConfig->eContent!=FTS5_CONTENT_NORMAL ){
 *pzErr = sqlite3_mprintf("multiple content=... directives");
 rc = SQLITE_ERROR;
 }else{
 if( zArg[0] ){
 pConfig->eContent = FTS5_CONTENT_EXTERNAL;
 pConfig->zContent = sqlite3Fts5Mprintf(&rc, "%Q.%Q", pConfig->zDb,zArg);
 }else{
 pConfig->eContent = FTS5_CONTENT_NONE;
 }
 }
 return rc;
 }

 if( sqlite3_strnicmp("contentless_delete", zCmd, nCmd)==0 ){
 if( (zArg[0]!='0' && zArg[0]!='1') || zArg[1]!='\0' ){
 *pzErr = sqlite3_mprintf("malformed contentless_delete=... directive");
 rc = SQLITE_ERROR;
 }else{
 pConfig->bContentlessDelete = (zArg[0]=='1');
 }
 return rc;
 }

 if( sqlite3_strnicmp("contentless_unindexed", zCmd, nCmd)==0 ){
 if( (zArg[0]!='0' && zArg[0]!='1') || zArg[1]!='\0' ){
 *pzErr = sqlite3_mprintf("malformed contentless_delete=... directive");
 rc = SQLITE_ERROR;
 }else{
 pConfig->bContentlessUnindexed = (zArg[0]=='1');
 }
 return rc;
 }

 if( sqlite3_strnicmp("content_rowid", zCmd, nCmd)==0 ){
 if( pConfig->zContentRowid ){
 *pzErr = sqlite3_mprintf("multiple content_rowid=... directives");
 rc = SQLITE_ERROR;
 }else{
 pConfig->zContentRowid = sqlite3Fts5Strndup(&rc, zArg, -1);
 }
 return rc;
 }

 if( sqlite3_strnicmp("columnsize", zCmd, nCmd)==0 ){
 if( (zArg[0]!='0' && zArg[0]!='1') || zArg[1]!='\0' ){
 *pzErr = sqlite3_mprintf("malformed columnsize=... directive");
 rc = SQLITE_ERROR;
 }else{
 pConfig->bColumnsize = (zArg[0]=='1');
 }
 return rc;
 }

 if( sqlite3_strnicmp("locale", zCmd, nCmd)==0 ){
 if( (zArg[0]!='0' && zArg[0]!='1') || zArg[1]!='\0' ){
 *pzErr = sqlite3_mprintf("malformed locale=... directive");
 rc = SQLITE_ERROR;
 }else{
 pConfig->bLocale = (zArg[0]=='1');
 }
 return rc;
 }

 if( sqlite3_strnicmp("detail", zCmd, nCmd)==0 ){
 const Fts5Enum aDetail[] = {
 { "none", FTS5_DETAIL_NONE },
 { "full", FTS5_DETAIL_FULL },
 { "columns", FTS5_DETAIL_COLUMNS },
 { 0, 0 }
 };

 if( (rc = fts5ConfigSetEnum(aDetail, zArg, &pConfig->eDetail)) ){
 *pzErr = sqlite3_mprintf("malformed detail=... directive");
 }
 return rc;
 }

 if( sqlite3_strnicmp("tokendata", zCmd, nCmd)==0 ){
 if( (zArg[0]!='0' && zArg[0]!='1') || zArg[1]!='\0' ){
 *pzErr = sqlite3_mprintf("malformed tokendata=... directive");
 rc = SQLITE_ERROR;
 }else{
 pConfig->bTokendata = (zArg[0]=='1');
 }
 return rc;
 }

 *pzErr = sqlite3_mprintf("unrecognized option: \"%.*s\"", nCmd, zCmd);
 return SQLITE_ERROR;
}

/*
** Gobble up the first bareword or quoted word from the input buffer zIn.
** Return a pointer to the character immediately following the last in
** the gobbled word if successful, or a NULL pointer otherwise (failed
** to find close-quote character).
**
** Before returning, set pzOut to point to a new buffer containing a
** nul-terminated, dequoted copy of the gobbled word. If the word was
** quoted, *pbQuoted is also set to 1 before returning.
**
** If *pRc is other than SQLITE_OK when this function is called, it is
** a no-op (NULL is returned). Otherwise, if an OOM occurs within this
** function, *pRc is set to SQLITE_NOMEM before returning. *pRc is *not*
** set if a parse error (failed to find close quote) occurs.
*/
static const char *fts5ConfigGobbleWord(
 int *pRc, /* IN/OUT: Error code */
 const char *zIn, /* Buffer to gobble string/bareword from */
 char **pzOut, /* OUT: malloc'd buffer containing str/bw */
 int *pbQuoted /* OUT: Set to true if dequoting required */
){
 const char *zRet = 0;

 sqlite3_int64 nIn = strlen(zIn);
 char *zOut = sqlite3_malloc64(nIn+1);

 assert( *pRc==SQLITE_OK );
 *pbQuoted = 0;
 *pzOut = 0;

 if( zOut==0 ){
 *pRc = SQLITE_NOMEM;
 }else{
 memcpy(zOut, zIn, (size_t)(nIn+1));
 if( fts5_isopenquote(zOut[0]) ){
 int ii = fts5Dequote(zOut);
 zRet = &zIn[ii];
 *pbQuoted = 1;
 }else{
 zRet = fts5ConfigSkipBareword(zIn);
 if( zRet ){
 zOut[zRet-zIn] = '\0';
 }
 }
 }

 if( zRet==0 ){
 sqlite3_free(zOut);
 }else{
 *pzOut = zOut;
 }

 return zRet;
}

static int fts5ConfigParseColumn(
 Fts5Config *p,
 char *zCol,
 char *zArg,
 char **pzErr,
 int *pbUnindexed
){
 int rc = SQLITE_OK;
 if( 0==sqlite3_stricmp(zCol, FTS5_RANK_NAME)
 || 0==sqlite3_stricmp(zCol, FTS5_ROWID_NAME)
 ){
 *pzErr = sqlite3_mprintf("reserved fts5 column name: %s", zCol);
 rc = SQLITE_ERROR;
 }else if( zArg ){
 if( 0==sqlite3_stricmp(zArg, "unindexed") ){
 p->abUnindexed[p->nCol] = 1;
 *pbUnindexed = 1;
 }else{
 *pzErr = sqlite3_mprintf("unrecognized column option: %s", zArg);
 rc = SQLITE_ERROR;
 }
 }

 p->azCol[p->nCol++] = zCol;
 return rc;
}

/*
** Populate the Fts5Config.zContentExprlist string.
*/
static int fts5ConfigMakeExprlist(Fts5Config *p){
 int i;
 int rc = SQLITE_OK;
 Fts5Buffer buf = {0, 0, 0};

 sqlite3Fts5BufferAppendPrintf(&rc, &buf, "T.%Q", p->zContentRowid);
 if( p->eContent!=FTS5_CONTENT_NONE ){
 assert( p->eContent==FTS5_CONTENT_EXTERNAL
 || p->eContent==FTS5_CONTENT_NORMAL
 || p->eContent==FTS5_CONTENT_UNINDEXED
 );
 for(i=0; i<p->nCol; i++){
 if( p->eContent==FTS5_CONTENT_EXTERNAL ){
 sqlite3Fts5BufferAppendPrintf(&rc, &buf, ", T.%Q", p->azCol[i]);
 }else if( p->eContent==FTS5_CONTENT_NORMAL || p->abUnindexed[i] ){
 sqlite3Fts5BufferAppendPrintf(&rc, &buf, ", T.c%d", i);
 }else{
 sqlite3Fts5BufferAppendPrintf(&rc, &buf, ", NULL");
 }
 }
 }
 if( p->eContent==FTS5_CONTENT_NORMAL && p->bLocale ){
 for(i=0; i<p->nCol; i++){
 if( p->abUnindexed[i]==0 ){
 sqlite3Fts5BufferAppendPrintf(&rc, &buf, ", T.l%d", i);
 }else{
 sqlite3Fts5BufferAppendPrintf(&rc, &buf, ", NULL");
 }
 }
 }

 assert( p->zContentExprlist==0 );
 p->zContentExprlist = (char*)buf.p;
 return rc;
}

/*
** Arguments nArg/azArg contain the string arguments passed to the xCreate
** or xConnect method of the virtual table. This function attempts to
** allocate an instance of Fts5Config containing the results of parsing
** those arguments.
**
** If successful, SQLITE_OK is returned and *ppOut is set to point to the
** new Fts5Config object. If an error occurs, an SQLite error code is
** returned, *ppOut is set to NULL and an error message may be left in
** *pzErr. It is the responsibility of the caller to eventually free any
** such error message using sqlite3_free().
*/
static int sqlite3Fts5ConfigParse(
 Fts5Global *pGlobal,
 sqlite3 *db,
 int nArg, /* Number of arguments */
 const char **azArg, /* Array of nArg CREATE VIRTUAL TABLE args */
 Fts5Config **ppOut, /* OUT: Results of parse */
 char **pzErr /* OUT: Error message */
){
 int rc = SQLITE_OK; /* Return code */
 Fts5Config *pRet; /* New object to return */
 int i;
 sqlite3_int64 nByte;
 int bUnindexed = 0; /* True if there are one or more UNINDEXED */

 *ppOut = pRet = (Fts5Config*)sqlite3_malloc(sizeof(Fts5Config));
 if( pRet==0 ) return SQLITE_NOMEM;
 memset(pRet, 0, sizeof(Fts5Config));
 pRet->pGlobal = pGlobal;
 pRet->db = db;
 pRet->iCookie = -1;

 nByte = nArg * (sizeof(char*) + sizeof(u8));
 pRet->azCol = (char**)sqlite3Fts5MallocZero(&rc, nByte);
 pRet->abUnindexed = pRet->azCol ? (u8*)&pRet->azCol[nArg] : 0;
 pRet->zDb = sqlite3Fts5Strndup(&rc, azArg[1], -1);
 pRet->zName = sqlite3Fts5Strndup(&rc, azArg[2], -1);
 pRet->bColumnsize = 1;
 pRet->eDetail = FTS5_DETAIL_FULL;
#ifdef SQLITE_DEBUG
 pRet->bPrefixIndex = 1;
#endif
 if( rc==SQLITE_OK && sqlite3_stricmp(pRet->zName, FTS5_RANK_NAME)==0 ){
 *pzErr = sqlite3_mprintf("reserved fts5 table name: %s", pRet->zName);
 rc = SQLITE_ERROR;
 }

 assert( (pRet->abUnindexed && pRet->azCol) || rc!=SQLITE_OK );
 for(i=3; rc==SQLITE_OK && i<nArg; i++){
 const char *zOrig = azArg[i];
 const char *z;
 char *zOne = 0;
 char *zTwo = 0;
 int bOption = 0;
 int bMustBeCol = 0;

 z = fts5ConfigGobbleWord(&rc, zOrig, &zOne, &bMustBeCol);
 z = fts5ConfigSkipWhitespace(z);
 if( z && *z=='=' ){
 bOption = 1;
 assert( zOne!=0 );
 z++;
 if( bMustBeCol ) z = 0;
 }
 z = fts5ConfigSkipWhitespace(z);
 if( z && z[0] ){
 int bDummy;
 z = fts5ConfigGobbleWord(&rc, z, &zTwo, &bDummy);
 if( z && z[0] ) z = 0;
 }

 if( rc==SQLITE_OK ){
 if( z==0 ){
 *pzErr = sqlite3_mprintf("parse error in \"%s\"", zOrig);
 rc = SQLITE_ERROR;
 }else{
 if( bOption ){
 rc = fts5ConfigParseSpecial(pRet,
 ALWAYS(zOne)?zOne:"",
 zTwo?zTwo:"",
 pzErr
 );
 }else{
 rc = fts5ConfigParseColumn(pRet, zOne, zTwo, pzErr, &bUnindexed);
 zOne = 0;
 }
 }
 }

 sqlite3_free(zOne);
 sqlite3_free(zTwo);
 }

 /* We only allow contentless_delete=1 if the table is indeed contentless. */
 if( rc==SQLITE_OK
 && pRet->bContentlessDelete
 && pRet->eContent!=FTS5_CONTENT_NONE
 ){
 *pzErr = sqlite3_mprintf(
 "contentless_delete=1 requires a contentless table"
 );
 rc = SQLITE_ERROR;
 }

 /* We only allow contentless_delete=1 if columnsize=0 is not present.
 **
 ** This restriction may be removed at some point.
 */
 if( rc==SQLITE_OK && pRet->bContentlessDelete && pRet->bColumnsize==0 ){
 *pzErr = sqlite3_mprintf(
 "contentless_delete=1 is incompatible with columnsize=0"
 );
 rc = SQLITE_ERROR;
 }

 /* We only allow contentless_unindexed=1 if the table is actually a
 ** contentless one.
 */
 if( rc==SQLITE_OK
 && pRet->bContentlessUnindexed
 && pRet->eContent!=FTS5_CONTENT_NONE
 ){
 *pzErr = sqlite3_mprintf(
 "contentless_unindexed=1 requires a contentless table"
 );
 rc = SQLITE_ERROR;
 }

 /* If no zContent option was specified, fill in the default values. */
 if( rc==SQLITE_OK && pRet->zContent==0 ){
 const char *zTail = 0;
 assert( pRet->eContent==FTS5_CONTENT_NORMAL
 || pRet->eContent==FTS5_CONTENT_NONE
 );
 if( pRet->eContent==FTS5_CONTENT_NORMAL ){
 zTail = "content";
 }else if( bUnindexed && pRet->bContentlessUnindexed ){
 pRet->eContent = FTS5_CONTENT_UNINDEXED;
 zTail = "content";
 }else if( pRet->bColumnsize ){
 zTail = "docsize";
 }

 if( zTail ){
 pRet->zContent = sqlite3Fts5Mprintf(
 &rc, "%Q.'%q_%s'", pRet->zDb, pRet->zName, zTail
 );
 }
 }

 if( rc==SQLITE_OK && pRet->zContentRowid==0 ){
 pRet->zContentRowid = sqlite3Fts5Strndup(&rc, "rowid", -1);
 }

 /* Formulate the zContentExprlist text */
 if( rc==SQLITE_OK ){
 rc = fts5ConfigMakeExprlist(pRet);
 }

 if( rc!=SQLITE_OK ){
 sqlite3Fts5ConfigFree(pRet);
 *ppOut = 0;
 }
 return rc;
}

/*
** Free the configuration object passed as the only argument.
*/
static void sqlite3Fts5ConfigFree(Fts5Config *pConfig){
 if( pConfig ){
 int i;
 if( pConfig->t.pTok ){
 if( pConfig->t.pApi1 ){
 pConfig->t.pApi1->xDelete(pConfig->t.pTok);
 }else{
 pConfig->t.pApi2->xDelete(pConfig->t.pTok);
 }
 }
 sqlite3_free((char*)pConfig->t.azArg);
 sqlite3_free(pConfig->zDb);
 sqlite3_free(pConfig->zName);
 for(i=0; i<pConfig->nCol; i++){
 sqlite3_free(pConfig->azCol[i]);
 }
 sqlite3_free(pConfig->azCol);
 sqlite3_free(pConfig->aPrefix);
 sqlite3_free(pConfig->zRank);
 sqlite3_free(pConfig->zRankArgs);
 sqlite3_free(pConfig->zContent);
 sqlite3_free(pConfig->zContentRowid);
 sqlite3_free(pConfig->zContentExprlist);
 sqlite3_free(pConfig);
 }
}

/*
** Call sqlite3_declare_vtab() based on the contents of the configuration
** object passed as the only argument. Return SQLITE_OK if successful, or
** an SQLite error code if an error occurs.
*/
static int sqlite3Fts5ConfigDeclareVtab(Fts5Config *pConfig){
 int i;
 int rc = SQLITE_OK;
 char *zSql;

 zSql = sqlite3Fts5Mprintf(&rc, "CREATE TABLE x(");
 for(i=0; zSql && i<pConfig->nCol; i++){
 const char *zSep = (i==0?"":", ");
 zSql = sqlite3Fts5Mprintf(&rc, "%z%s%Q", zSql, zSep, pConfig->azCol[i]);
 }
 zSql = sqlite3Fts5Mprintf(&rc, "%z, %Q HIDDEN, %s HIDDEN)",
 zSql, pConfig->zName, FTS5_RANK_NAME
 );

 assert( zSql || rc==SQLITE_NOMEM );
 if( zSql ){
 rc = sqlite3_declare_vtab(pConfig->db, zSql);
 sqlite3_free(zSql);
 }

 return rc;
}

/*
** Tokenize the text passed via the second and third arguments.
**
** The callback is invoked once for each token in the input text. The
** arguments passed to it are, in order:
**
** void *pCtx // Copy of 4th argument to sqlite3Fts5Tokenize()
** const char *pToken // Pointer to buffer containing token
** int nToken // Size of token in bytes
** int iStart // Byte offset of start of token within input text
** int iEnd // Byte offset of end of token within input text
** int iPos // Position of token in input (first token is 0)
**
** If the callback returns a non-zero value the tokenization is abandoned
** and no further callbacks are issued.
**
** This function returns SQLITE_OK if successful or an SQLite error code
** if an error occurs. If the tokenization was abandoned early because
** the callback returned SQLITE_DONE, this is not an error and this function
** still returns SQLITE_OK. Or, if the tokenization was abandoned early
** because the callback returned another non-zero value, it is assumed
** to be an SQLite error code and returned to the caller.
*/
static int sqlite3Fts5Tokenize(
 Fts5Config *pConfig, /* FTS5 Configuration object */
 int flags, /* FTS5_TOKENIZE_* flags */
 const char *pText, int nText, /* Text to tokenize */
 void *pCtx, /* Context passed to xToken() */
 int (*xToken)(void*, int, const char*, int, int, int) /* Callback */
){
 int rc = SQLITE_OK;
 if( pText ){
 if( pConfig->t.pTok==0 ){
 rc = sqlite3Fts5LoadTokenizer(pConfig);
 }
 if( rc==SQLITE_OK ){
 if( pConfig->t.pApi1 ){
 rc = pConfig->t.pApi1->xTokenize(
 pConfig->t.pTok, pCtx, flags, pText, nText, xToken
 );
 }else{
 rc = pConfig->t.pApi2->xTokenize(pConfig->t.pTok, pCtx, flags,
 pText, nText, pConfig->t.pLocale, pConfig->t.nLocale, xToken
 );
 }
 }
 }
 return rc;
}

/*
** Argument pIn points to the first character in what is expected to be
** a comma-separated list of SQL literals followed by a ')' character.
** If it actually is this, return a pointer to the ')'. Otherwise, return
** NULL to indicate a parse error.
*/
static const char *fts5ConfigSkipArgs(const char *pIn){
 const char *p = pIn;

 while( 1 ){
 p = fts5ConfigSkipWhitespace(p);
 p = fts5ConfigSkipLiteral(p);
 p = fts5ConfigSkipWhitespace(p);
 if( p==0 || *p==')' ) break;
 if( *p!=',' ){
 p = 0;
 break;
 }
 p++;
 }

 return p;
}

/*
** Parameter zIn contains a rank() function specification. The format of
** this is:
**
** + Bareword (function name)
** + Open parenthesis - "("
** + Zero or more SQL literals in a comma separated list
** + Close parenthesis - ")"
*/
static int sqlite3Fts5ConfigParseRank(
 const char *zIn, /* Input string */
 char **pzRank, /* OUT: Rank function name */
 char **pzRankArgs /* OUT: Rank function arguments */
){
 const char *p = zIn;
 const char *pRank;
 char *zRank = 0;
 char *zRankArgs = 0;
 int rc = SQLITE_OK;

 *pzRank = 0;
 *pzRankArgs = 0;

 if( p==0 ){
 rc = SQLITE_ERROR;
 }else{
 p = fts5ConfigSkipWhitespace(p);
 pRank = p;
 p = fts5ConfigSkipBareword(p);

 if( p ){
 zRank = sqlite3Fts5MallocZero(&rc, 1 + p - pRank);
 if( zRank ) memcpy(zRank, pRank, p-pRank);
 }else{
 rc = SQLITE_ERROR;
 }

 if( rc==SQLITE_OK ){
 p = fts5ConfigSkipWhitespace(p);
 if( *p!='(' ) rc = SQLITE_ERROR;
 p++;
 }
 if( rc==SQLITE_OK ){
 const char *pArgs;
 p = fts5ConfigSkipWhitespace(p);
 pArgs = p;
 if( *p!=')' ){
 p = fts5ConfigSkipArgs(p);
 if( p==0 ){
 rc = SQLITE_ERROR;
 }else{
 zRankArgs = sqlite3Fts5MallocZero(&rc, 1 + p - pArgs);
 if( zRankArgs ) memcpy(zRankArgs, pArgs, p-pArgs);
 }
 }
 }
 }

 if( rc!=SQLITE_OK ){
 sqlite3_free(zRank);
 assert( zRankArgs==0 );
 }else{
 *pzRank = zRank;
 *pzRankArgs = zRankArgs;
 }
 return rc;
}

static int sqlite3Fts5ConfigSetValue(
 Fts5Config *pConfig,
 const char *zKey,
 sqlite3_value *pVal,
 int *pbBadkey
){
 int rc = SQLITE_OK;

 if( 0==sqlite3_stricmp(zKey, "pgsz") ){
 int pgsz = 0;
 if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
 pgsz = sqlite3_value_int(pVal);
 }
 if( pgsz<32 || pgsz>FTS5_MAX_PAGE_SIZE ){
 *pbBadkey = 1;
 }else{
 pConfig->pgsz = pgsz;
 }
 }

 else if( 0==sqlite3_stricmp(zKey, "hashsize") ){
 int nHashSize = -1;
 if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
 nHashSize = sqlite3_value_int(pVal);
 }
 if( nHashSize<=0 ){
 *pbBadkey = 1;
 }else{
 pConfig->nHashSize = nHashSize;
 }
 }

 else if( 0==sqlite3_stricmp(zKey, "automerge") ){
 int nAutomerge = -1;
 if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
 nAutomerge = sqlite3_value_int(pVal);
 }
 if( nAutomerge<0 || nAutomerge>64 ){
 *pbBadkey = 1;
 }else{
 if( nAutomerge==1 ) nAutomerge = FTS5_DEFAULT_AUTOMERGE;
 pConfig->nAutomerge = nAutomerge;
 }
 }

 else if( 0==sqlite3_stricmp(zKey, "usermerge") ){
 int nUsermerge = -1;
 if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
 nUsermerge = sqlite3_value_int(pVal);
 }
 if( nUsermerge<2 || nUsermerge>16 ){
 *pbBadkey = 1;
 }else{
 pConfig->nUsermerge = nUsermerge;
 }
 }

 else if( 0==sqlite3_stricmp(zKey, "crisismerge") ){
 int nCrisisMerge = -1;
 if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
 nCrisisMerge = sqlite3_value_int(pVal);
 }
 if( nCrisisMerge<0 ){
 *pbBadkey = 1;
 }else{
 if( nCrisisMerge<=1 ) nCrisisMerge = FTS5_DEFAULT_CRISISMERGE;
 if( nCrisisMerge>=FTS5_MAX_SEGMENT ) nCrisisMerge = FTS5_MAX_SEGMENT-1;
 pConfig->nCrisisMerge = nCrisisMerge;
 }
 }

 else if( 0==sqlite3_stricmp(zKey, "deletemerge") ){
 int nVal = -1;
 if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
 nVal = sqlite3_value_int(pVal);
 }else{
 *pbBadkey = 1;
 }
 if( nVal<0 ) nVal = FTS5_DEFAULT_DELETE_AUTOMERGE;
 if( nVal>100 ) nVal = 0;
 pConfig->nDeleteMerge = nVal;
 }

 else if( 0==sqlite3_stricmp(zKey, "rank") ){
 const char *zIn = (const char*)sqlite3_value_text(pVal);
 char *zRank;
 char *zRankArgs;
 rc = sqlite3Fts5ConfigParseRank(zIn, &zRank, &zRankArgs);
 if( rc==SQLITE_OK ){
 sqlite3_free(pConfig->zRank);
 sqlite3_free(pConfig->zRankArgs);
 pConfig->zRank = zRank;
 pConfig->zRankArgs = zRankArgs;
 }else if( rc==SQLITE_ERROR ){
 rc = SQLITE_OK;
 *pbBadkey = 1;
 }
 }

 else if( 0==sqlite3_stricmp(zKey, "secure-delete") ){
 int bVal = -1;
 if( SQLITE_INTEGER==sqlite3_value_numeric_type(pVal) ){
 bVal = sqlite3_value_int(pVal);
 }
 if( bVal<0 ){
 *pbBadkey = 1;
 }else{
 pConfig->bSecureDelete = (bVal ? 1 : 0);
 }
 }else{
 *pbBadkey = 1;
 }
 return rc;
}

/*
** Load the contents of the %_config table into memory.
*/
static int sqlite3Fts5ConfigLoad(Fts5Config *pConfig, int iCookie){
 const char *zSelect = "SELECT k, v FROM %Q.'%q_config'";
 char *zSql;
 sqlite3_stmt *p = 0;
 int rc = SQLITE_OK;
 int iVersion = 0;

 /* Set default values */
 pConfig->pgsz = FTS5_DEFAULT_PAGE_SIZE;
 pConfig->nAutomerge = FTS5_DEFAULT_AUTOMERGE;
 pConfig->nUsermerge = FTS5_DEFAULT_USERMERGE;
 pConfig->nCrisisMerge = FTS5_DEFAULT_CRISISMERGE;
 pConfig->nHashSize = FTS5_DEFAULT_HASHSIZE;
 pConfig->nDeleteMerge = FTS5_DEFAULT_DELETE_AUTOMERGE;

 zSql = sqlite3Fts5Mprintf(&rc, zSelect, pConfig->zDb, pConfig->zName);
 if( zSql ){
 rc = sqlite3_prepare_v2(pConfig->db, zSql, -1, &p, 0);
 sqlite3_free(zSql);
 }

 assert( rc==SQLITE_OK || p==0 );
 if( rc==SQLITE_OK ){
 while( SQLITE_ROW==sqlite3_step(p) ){
 const char *zK = (const char*)sqlite3_column_text(p, 0);
 sqlite3_value *pVal = sqlite3_column_value(p, 1);
 if( 0==sqlite3_stricmp(zK, "version") ){
 iVersion = sqlite3_value_int(pVal);
 }else{
 int bDummy = 0;
 sqlite3Fts5ConfigSetValue(pConfig, zK, pVal, &bDummy);
 }
 }
 rc = sqlite3_finalize(p);
 }

 if( rc==SQLITE_OK
 && iVersion!=FTS5_CURRENT_VERSION
 && iVersion!=FTS5_CURRENT_VERSION_SECUREDELETE
 ){
 rc = SQLITE_ERROR;
 sqlite3Fts5ConfigErrmsg(pConfig, "invalid fts5 file format "
 "(found %d, expected %d or %d) - run 'rebuild'",
 iVersion, FTS5_CURRENT_VERSION, FTS5_CURRENT_VERSION_SECUREDELETE
 );
 }else{
 pConfig->iVersion = iVersion;
 }

 if( rc==SQLITE_OK ){
 pConfig->iCookie = iCookie;
 }
 return rc;
}

/*
** Set (*pConfig->pzErrmsg) to point to an sqlite3_malloc()ed buffer
** containing the error message created using printf() style formatting
** string zFmt and its trailing arguments.
*/
static void sqlite3Fts5ConfigErrmsg(Fts5Config *pConfig, const char *zFmt, ...){
 va_list ap; /* ... printf arguments */
 char *zMsg = 0;

 va_start(ap, zFmt);
 zMsg = sqlite3_vmprintf(zFmt, ap);
 if( pConfig->pzErrmsg ){
 assert( *pConfig->pzErrmsg==0 );
 *pConfig->pzErrmsg = zMsg;
 }else{
 sqlite3_free(zMsg);
 }

 va_end(ap);
}

#line 1 "fts5_expr.c"
/*
** 2014 May 31
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
*/

/* #include "fts5Int.h" */
/* #include "fts5parse.h" */

#ifndef SQLITE_FTS5_MAX_EXPR_DEPTH
# define SQLITE_FTS5_MAX_EXPR_DEPTH 256
#endif

/*
** All token types in the generated fts5parse.h file are greater than 0.
*/
#define FTS5_EOF 0

#define FTS5_LARGEST_INT64 (0xffffffff|(((i64)0x7fffffff)<<32))

typedef struct Fts5ExprTerm Fts5ExprTerm;

/*
** Functions generated by lemon from fts5parse.y.
*/
static void *sqlite3Fts5ParserAlloc(void *(*mallocProc)(u64));
static void sqlite3Fts5ParserFree(void*, void (*freeProc)(void*));
static void sqlite3Fts5Parser(void*, int, Fts5Token, Fts5Parse*);
#ifndef NDEBUG
#include <stdio.h>
static void sqlite3Fts5ParserTrace(FILE*, char*);
#endif
static int sqlite3Fts5ParserFallback(int);

struct Fts5Expr {
 Fts5Index *pIndex;
 Fts5Config *pConfig;
 Fts5ExprNode *pRoot;
 int bDesc; /* Iterate in descending rowid order */
 int nPhrase; /* Number of phrases in expression */
 Fts5ExprPhrase **apExprPhrase; /* Pointers to phrase objects */
};

/*
** eType:
** Expression node type. Usually one of:
**
** FTS5_AND (nChild, apChild valid)
** FTS5_OR (nChild, apChild valid)
** FTS5_NOT (nChild, apChild valid)
** FTS5_STRING (pNear valid)
** FTS5_TERM (pNear valid)
**
** An expression node with eType==0 may also exist. It always matches zero
** rows. This is created when a phrase containing no tokens is parsed.
** e.g. "".
**
** iHeight:
** Distance from this node to furthest leaf. This is always 0 for nodes
** of type FTS5_STRING and FTS5_TERM. For all other nodes it is one
** greater than the largest child value.
*/
struct Fts5ExprNode {
 int eType; /* Node type */
 int bEof; /* True at EOF */
 int bNomatch; /* True if entry is not a match */
 int iHeight; /* Distance to tree leaf nodes */

 /* Next method for this node. */
 int (*xNext)(Fts5Expr*, Fts5ExprNode*, int, i64);

 i64 iRowid; /* Current rowid */
 Fts5ExprNearset *pNear; /* For FTS5_STRING - cluster of phrases */

 /* Child nodes. For a NOT node, this array always contains 2 entries. For
 ** AND or OR nodes, it contains 2 or more entries. */
 int nChild; /* Number of child nodes */
 Fts5ExprNode *apChild[1]; /* Array of child nodes */
};

#define Fts5NodeIsString(p) ((p)->eType==FTS5_TERM || (p)->eType==FTS5_STRING)

/*
** Invoke the xNext method of an Fts5ExprNode object. This macro should be
** used as if it has the same signature as the xNext() methods themselves.
*/
#define fts5ExprNodeNext(a,b,c,d) (b)->xNext((a), (b), (c), (d))

/*
** An instance of the following structure represents a single search term
** or term prefix.
*/
struct Fts5ExprTerm {
 u8 bPrefix; /* True for a prefix term */
 u8 bFirst; /* True if token must be first in column */
 char *pTerm; /* Term data */
 int nQueryTerm; /* Effective size of term in bytes */
 int nFullTerm; /* Size of term in bytes incl. tokendata */
 Fts5IndexIter *pIter; /* Iterator for this term */
 Fts5ExprTerm *pSynonym; /* Pointer to first in list of synonyms */
};

/*
** A phrase. One or more terms that must appear in a contiguous sequence
** within a document for it to match.
*/
struct Fts5ExprPhrase {
 Fts5ExprNode *pNode; /* FTS5_STRING node this phrase is part of */
 Fts5Buffer poslist; /* Current position list */
 int nTerm; /* Number of entries in aTerm[] */
 Fts5ExprTerm aTerm[1]; /* Terms that make up this phrase */
};

/*
** One or more phrases that must appear within a certain token distance of
** each other within each matching document.
*/
struct Fts5ExprNearset {
 int nNear; /* NEAR parameter */
 Fts5Colset *pColset; /* Columns to search (NULL -> all columns) */
 int nPhrase; /* Number of entries in aPhrase[] array */
 Fts5ExprPhrase *apPhrase[1]; /* Array of phrase pointers */
};

/*
** Parse context.
*/
struct Fts5Parse {
 Fts5Config *pConfig;
 char *zErr;
 int rc;
 int nPhrase; /* Size of apPhrase array */
 Fts5ExprPhrase **apPhrase; /* Array of all phrases */
 Fts5ExprNode *pExpr; /* Result of a successful parse */
 int bPhraseToAnd; /* Convert "a+b" to "a AND b" */
};

/*
** Check that the Fts5ExprNode.iHeight variables are set correctly in
** the expression tree passed as the only argument.
*/
#ifndef NDEBUG
static void assert_expr_depth_ok(int rc, Fts5ExprNode *p){
 if( rc==SQLITE_OK ){
 if( p->eType==FTS5_TERM || p->eType==FTS5_STRING || p->eType==0 ){
 assert( p->iHeight==0 );
 }else{
 int ii;
 int iMaxChild = 0;
 for(ii=0; ii<p->nChild; ii++){
 Fts5ExprNode *pChild = p->apChild[ii];
 iMaxChild = MAX(iMaxChild, pChild->iHeight);
 assert_expr_depth_ok(SQLITE_OK, pChild);
 }
 assert( p->iHeight==iMaxChild+1 );
 }
 }
}
#else
# define assert_expr_depth_ok(rc, p)
#endif

static void sqlite3Fts5ParseError(Fts5Parse *pParse, const char *zFmt, ...){
 va_list ap;
 va_start(ap, zFmt);
 if( pParse->rc==SQLITE_OK ){
 assert( pParse->zErr==0 );
 pParse->zErr = sqlite3_vmprintf(zFmt, ap);
 pParse->rc = SQLITE_ERROR;
 }
 va_end(ap);
}

static int fts5ExprIsspace(char t){
 return t==' ' || t=='\t' || t=='\n' || t=='\r';
}

/*
** Read the first token from the nul-terminated string at *pz.
*/
static int fts5ExprGetToken(
 Fts5Parse *pParse,
 const char **pz, /* IN/OUT: Pointer into buffer */
 Fts5Token *pToken
){
 const char *z = *pz;
 int tok;

 /* Skip past any whitespace */
 while( fts5ExprIsspace(*z) ) z++;

 pToken->p = z;
 pToken->n = 1;
 switch( *z ){
 case '(': tok = FTS5_LP; break;
 case ')': tok = FTS5_RP; break;
 case '{': tok = FTS5_LCP; break;
 case '}': tok = FTS5_RCP; break;
 case ':': tok = FTS5_COLON; break;
 case ',': tok = FTS5_COMMA; break;
 case '+': tok = FTS5_PLUS; break;
 case '*': tok = FTS5_STAR; break;
 case '-': tok = FTS5_MINUS; break;
 case '^': tok = FTS5_CARET; break;
 case '\0': tok = FTS5_EOF; break;

 case '"': {
 const char *z2;
 tok = FTS5_STRING;

 for(z2=&z[1]; 1; z2++){
 if( z2[0]=='"' ){
 z2++;
 if( z2[0]!='"' ) break;
 }
 if( z2[0]=='\0' ){
 sqlite3Fts5ParseError(pParse, "unterminated string");
 return FTS5_EOF;
 }
 }
 pToken->n = (z2 - z);
 break;
 }

 default: {
 const char *z2;
 if( sqlite3Fts5IsBareword(z[0])==0 ){
 sqlite3Fts5ParseError(pParse, "fts5: syntax error near \"%.1s\"", z);
 return FTS5_EOF;
 }
 tok = FTS5_STRING;
 for(z2=&z[1]; sqlite3Fts5IsBareword(*z2); z2++);
 pToken->n = (z2 - z);
 if( pToken->n==2 && memcmp(pToken->p, "OR", 2)==0 ) tok = FTS5_OR;
 if( pToken->n==3 && memcmp(pToken->p, "NOT", 3)==0 ) tok = FTS5_NOT;
 if( pToken->n==3 && memcmp(pToken->p, "AND", 3)==0 ) tok = FTS5_AND;
 break;
 }
 }

 *pz = &pToken->p[pToken->n];
 return tok;
}

static void *fts5ParseAlloc(u64 t){ return sqlite3_malloc64((sqlite3_int64)t);}
static void fts5ParseFree(void *p){ sqlite3_free(p); }

static int sqlite3Fts5ExprNew(
 Fts5Config *pConfig, /* FTS5 Configuration */
 int bPhraseToAnd,
 int iCol,
 const char *zExpr, /* Expression text */
 Fts5Expr **ppNew,
 char **pzErr
){
 Fts5Parse sParse;
 Fts5Token token;
 const char *z = zExpr;
 int t; /* Next token type */
 void *pEngine;
 Fts5Expr *pNew;

 *ppNew = 0;
 *pzErr = 0;
 memset(&sParse, 0, sizeof(sParse));
 sParse.bPhraseToAnd = bPhraseToAnd;
 pEngine = sqlite3Fts5ParserAlloc(fts5ParseAlloc);
 if( pEngine==0 ){ return SQLITE_NOMEM; }
 sParse.pConfig = pConfig;

 do {
 t = fts5ExprGetToken(&sParse, &z, &token);
 sqlite3Fts5Parser(pEngine, t, token, &sParse);
 }while( sParse.rc==SQLITE_OK && t!=FTS5_EOF );
 sqlite3Fts5ParserFree(pEngine, fts5ParseFree);

 assert( sParse.pExpr || sParse.rc!=SQLITE_OK );
 assert_expr_depth_ok(sParse.rc, sParse.pExpr);

 /* If the LHS of the MATCH expression was a user column, apply the
 ** implicit column-filter. */
 if( sParse.rc==SQLITE_OK && iCol<pConfig->nCol ){
 int n = sizeof(Fts5Colset);
 Fts5Colset *pColset = (Fts5Colset*)sqlite3Fts5MallocZero(&sParse.rc, n);
 if( pColset ){
 pColset->nCol = 1;
 pColset->aiCol[0] = iCol;
 sqlite3Fts5ParseSetColset(&sParse, sParse.pExpr, pColset);
 }
 }

 assert( sParse.rc!=SQLITE_OK || sParse.zErr==0 );
 if( sParse.rc==SQLITE_OK ){
 *ppNew = pNew = sqlite3_malloc(sizeof(Fts5Expr));
 if( pNew==0 ){
 sParse.rc = SQLITE_NOMEM;
 sqlite3Fts5ParseNodeFree(sParse.pExpr);
 }else{
 pNew->pRoot = sParse.pExpr;
 pNew->pIndex = 0;
 pNew->pConfig = pConfig;
 pNew->apExprPhrase = sParse.apPhrase;
 pNew->nPhrase = sParse.nPhrase;
 pNew->bDesc = 0;
 sParse.apPhrase = 0;
 }
 }else{
 sqlite3Fts5ParseNodeFree(sParse.pExpr);
 }

 sqlite3_free(sParse.apPhrase);
 if( 0==*pzErr ){
 *pzErr = sParse.zErr;
 }else{
 sqlite3_free(sParse.zErr);
 }
 return sParse.rc;
}

/*
** Assuming that buffer z is at least nByte bytes in size and contains a
** valid utf-8 string, return the number of characters in the string.
*/
static int fts5ExprCountChar(const char *z, int nByte){
 int nRet = 0;
 int ii;
 for(ii=0; ii<nByte; ii++){
 if( (z[ii] & 0xC0)!=0x80 ) nRet++;
 }
 return nRet;
}

/*
** This function is only called when using the special 'trigram' tokenizer.
** Argument zText contains the text of a LIKE or GLOB pattern matched
** against column iCol. This function creates and compiles an FTS5 MATCH
** expression that will match a superset of the rows matched by the LIKE or
** GLOB. If successful, SQLITE_OK is returned. Otherwise, an SQLite error
** code.
*/
static int sqlite3Fts5ExprPattern(
 Fts5Config *pConfig, int bGlob, int iCol, const char *zText, Fts5Expr **pp
){
 i64 nText = strlen(zText);
 char *zExpr = (char*)sqlite3_malloc64(nText*4 + 1);
 int rc = SQLITE_OK;

 if( zExpr==0 ){
 rc = SQLITE_NOMEM;
 }else{
 char aSpec[3];
 int iOut = 0;
 int i = 0;
 int iFirst = 0;

 if( bGlob==0 ){
 aSpec[0] = '_';
 aSpec[1] = '%';
 aSpec[2] = 0;
 }else{
 aSpec[0] = '*';
 aSpec[1] = '?';
 aSpec[2] = '[';
 }

 while( i<=nText ){
 if( i==nText
 || zText[i]==aSpec[0] || zText[i]==aSpec[1] || zText[i]==aSpec[2]
 ){

 if( fts5ExprCountChar(&zText[iFirst], i-iFirst)>=3 ){
 int jj;
 zExpr[iOut++] = '"';
 for(jj=iFirst; jj<i; jj++){
 zExpr[iOut++] = zText[jj];
 if( zText[jj]=='"' ) zExpr[iOut++] = '"';
 }
 zExpr[iOut++] = '"';
 zExpr[iOut++] = ' ';
 }
 if( zText[i]==aSpec[2] ){
 i += 2;
 if( zText[i-1]=='^' ) i++;
 while( i<nText && zText[i]!=']' ) i++;
 }
 iFirst = i+1;
 }
 i++;
 }
 if( iOut>0 ){
 int bAnd = 0;
 if( pConfig->eDetail!=FTS5_DETAIL_FULL ){
 bAnd = 1;
 if( pConfig->eDetail==FTS5_DETAIL_NONE ){
 iCol = pConfig->nCol;
 }
 }
 zExpr[iOut] = '\0';
 rc = sqlite3Fts5ExprNew(pConfig, bAnd, iCol, zExpr, pp,pConfig->pzErrmsg);
 }else{
 *pp = 0;
 }
 sqlite3_free(zExpr);
 }

 return rc;
}

/*
** Free the expression node object passed as the only argument.
*/
static void sqlite3Fts5ParseNodeFree(Fts5ExprNode *p){
 if( p ){
 int i;
 for(i=0; i<p->nChild; i++){
 sqlite3Fts5ParseNodeFree(p->apChild[i]);
 }
 sqlite3Fts5ParseNearsetFree(p->pNear);
 sqlite3_free(p);
 }
}

/*
** Free the expression object passed as the only argument.
*/
static void sqlite3Fts5ExprFree(Fts5Expr *p){
 if( p ){
 sqlite3Fts5ParseNodeFree(p->pRoot);
 sqlite3_free(p->apExprPhrase);
 sqlite3_free(p);
 }
}

static int sqlite3Fts5ExprAnd(Fts5Expr **pp1, Fts5Expr *p2){
 Fts5Parse sParse;
 memset(&sParse, 0, sizeof(sParse));

 if( *pp1 && p2 ){
 Fts5Expr *p1 = *pp1;
 int nPhrase = p1->nPhrase + p2->nPhrase;

 p1->pRoot = sqlite3Fts5ParseNode(&sParse, FTS5_AND, p1->pRoot, p2->pRoot,0);
 p2->pRoot = 0;

 if( sParse.rc==SQLITE_OK ){
 Fts5ExprPhrase **ap = (Fts5ExprPhrase**)sqlite3_realloc(
 p1->apExprPhrase, nPhrase * sizeof(Fts5ExprPhrase*)
 );
 if( ap==0 ){
 sParse.rc = SQLITE_NOMEM;
 }else{
 int i;
 memmove(&ap[p2->nPhrase], ap, p1->nPhrase*sizeof(Fts5ExprPhrase*));
 for(i=0; i<p2->nPhrase; i++){
 ap[i] = p2->apExprPhrase[i];
 }
 p1->nPhrase = nPhrase;
 p1->apExprPhrase = ap;
 }
 }
 sqlite3_free(p2->apExprPhrase);
 sqlite3_free(p2);
 }else if( p2 ){
 *pp1 = p2;
 }

 return sParse.rc;
}

/*
** Argument pTerm must be a synonym iterator. Return the current rowid
** that it points to.
*/
static i64 fts5ExprSynonymRowid(Fts5ExprTerm *pTerm, int bDesc, int *pbEof){
 i64 iRet = 0;
 int bRetValid = 0;
 Fts5ExprTerm *p;

 assert( pTerm );
 assert( pTerm->pSynonym );
 assert( bDesc==0 || bDesc==1 );
 for(p=pTerm; p; p=p->pSynonym){
 if( 0==sqlite3Fts5IterEof(p->pIter) ){
 i64 iRowid = p->pIter->iRowid;
 if( bRetValid==0 || (bDesc!=(iRowid<iRet)) ){
 iRet = iRowid;
 bRetValid = 1;
 }
 }
 }

 if( pbEof && bRetValid==0 ) *pbEof = 1;
 return iRet;
}

/*
** Argument pTerm must be a synonym iterator.
*/
static int fts5ExprSynonymList(
 Fts5ExprTerm *pTerm,
 i64 iRowid,
 Fts5Buffer *pBuf, /* Use this buffer for space if required */
 u8 **pa, int *pn
){
 Fts5PoslistReader aStatic[4];
 Fts5PoslistReader *aIter = aStatic;
 int nIter = 0;
 int nAlloc = 4;
 int rc = SQLITE_OK;
 Fts5ExprTerm *p;

 assert( pTerm->pSynonym );
 for(p=pTerm; p; p=p->pSynonym){
 Fts5IndexIter *pIter = p->pIter;
 if( sqlite3Fts5IterEof(pIter)==0 && pIter->iRowid==iRowid ){
 if( pIter->nData==0 ) continue;
 if( nIter==nAlloc ){
 sqlite3_int64 nByte = sizeof(Fts5PoslistReader) * nAlloc * 2;
 Fts5PoslistReader *aNew = (Fts5PoslistReader*)sqlite3_malloc64(nByte);
 if( aNew==0 ){
 rc = SQLITE_NOMEM;
 goto synonym_poslist_out;
 }
 memcpy(aNew, aIter, sizeof(Fts5PoslistReader) * nIter);
 nAlloc = nAlloc*2;
 if( aIter!=aStatic ) sqlite3_free(aIter);
 aIter = aNew;
 }
 sqlite3Fts5PoslistReaderInit(pIter->pData, pIter->nData, &aIter[nIter]);
 assert( aIter[nIter].bEof==0 );
 nIter++;
 }
 }

 if( nIter==1 ){
 *pa = (u8*)aIter[0].a;
 *pn = aIter[0].n;
 }else{
 Fts5PoslistWriter writer = {0};
 i64 iPrev = -1;
 fts5BufferZero(pBuf);
 while( 1 ){
 int i;
 i64 iMin = FTS5_LARGEST_INT64;
 for(i=0; i<nIter; i++){
 if( aIter[i].bEof==0 ){
 if( aIter[i].iPos==iPrev ){
 if( sqlite3Fts5PoslistReaderNext(&aIter[i]) ) continue;
 }
 if( aIter[i].iPos<iMin ){
 iMin = aIter[i].iPos;
 }
 }
 }
 if( iMin==FTS5_LARGEST_INT64 || rc!=SQLITE_OK ) break;
 rc = sqlite3Fts5PoslistWriterAppend(pBuf, &writer, iMin);
 iPrev = iMin;
 }
 if( rc==SQLITE_OK ){
 *pa = pBuf->p;
 *pn = pBuf->n;
 }
 }

synonym_poslist_out:
 if( aIter!=aStatic ) sqlite3_free(aIter);
 return rc;
}

/*
** All individual term iterators in pPhrase are guaranteed to be valid and
** pointing to the same rowid when this function is called. This function
** checks if the current rowid really is a match, and if so populates
** the pPhrase->poslist buffer accordingly. Output parameter *pbMatch
** is set to true if this is really a match, or false otherwise.
**
** SQLITE_OK is returned if an error occurs, or an SQLite error code
** otherwise. It is not considered an error code if the current rowid is
** not a match.
*/
static int fts5ExprPhraseIsMatch(
 Fts5ExprNode *pNode, /* Node pPhrase belongs to */
 Fts5ExprPhrase *pPhrase, /* Phrase object to initialize */
 int *pbMatch /* OUT: Set to true if really a match */
){
 Fts5PoslistWriter writer = {0};
 Fts5PoslistReader aStatic[4];
 Fts5PoslistReader *aIter = aStatic;
 int i;
 int rc = SQLITE_OK;
 int bFirst = pPhrase->aTerm[0].bFirst;

 fts5BufferZero(&pPhrase->poslist);

 /* If the aStatic[] array is not large enough, allocate a large array
 ** using sqlite3_malloc(). This approach could be improved upon. */
 if( pPhrase->nTerm>ArraySize(aStatic) ){
 sqlite3_int64 nByte = sizeof(Fts5PoslistReader) * pPhrase->nTerm;
 aIter = (Fts5PoslistReader*)sqlite3_malloc64(nByte);
 if( !aIter ) return SQLITE_NOMEM;
 }
 memset(aIter, 0, sizeof(Fts5PoslistReader) * pPhrase->nTerm);

 /* Initialize a term iterator for each term in the phrase */
 for(i=0; i<pPhrase->nTerm; i++){
 Fts5ExprTerm *pTerm = &pPhrase->aTerm[i];
 int n = 0;
 int bFlag = 0;
 u8 *a = 0;
 if( pTerm->pSynonym ){
 Fts5Buffer buf = {0, 0, 0};
 rc = fts5ExprSynonymList(pTerm, pNode->iRowid, &buf, &a, &n);
 if( rc ){
 sqlite3_free(a);
 goto ismatch_out;
 }
 if( a==buf.p ) bFlag = 1;
 }else{
 a = (u8*)pTerm->pIter->pData;
 n = pTerm->pIter->nData;
 }
 sqlite3Fts5PoslistReaderInit(a, n, &aIter[i]);
 aIter[i].bFlag = (u8)bFlag;
 if( aIter[i].bEof ) goto ismatch_out;
 }

 while( 1 ){
 int bMatch;
 i64 iPos = aIter[0].iPos;
 do {
 bMatch = 1;
 for(i=0; i<pPhrase->nTerm; i++){
 Fts5PoslistReader *pPos = &aIter[i];
 i64 iAdj = iPos + i;
 if( pPos->iPos!=iAdj ){
 bMatch = 0;
 while( pPos->iPos<iAdj ){
 if( sqlite3Fts5PoslistReaderNext(pPos) ) goto ismatch_out;
 }
 if( pPos->iPos>iAdj ) iPos = pPos->iPos-i;
 }
 }
 }while( bMatch==0 );

 /* Append position iPos to the output */
 if( bFirst==0 || FTS5_POS2OFFSET(iPos)==0 ){
 rc = sqlite3Fts5PoslistWriterAppend(&pPhrase->poslist, &writer, iPos);
 if( rc!=SQLITE_OK ) goto ismatch_out;
 }

 for(i=0; i<pPhrase->nTerm; i++){
 if( sqlite3Fts5PoslistReaderNext(&aIter[i]) ) goto ismatch_out;
 }
 }

ismatch_out:
 *pbMatch = (pPhrase->poslist.n>0);
 for(i=0; i<pPhrase->nTerm; i++){
 if( aIter[i].bFlag ) sqlite3_free((u8*)aIter[i].a);
 }
 if( aIter!=aStatic ) sqlite3_free(aIter);
 return rc;
}

typedef struct Fts5LookaheadReader Fts5LookaheadReader;
struct Fts5LookaheadReader {
 const u8 *a; /* Buffer containing position list */
 int n; /* Size of buffer a[] in bytes */
 int i; /* Current offset in position list */
 i64 iPos; /* Current position */
 i64 iLookahead; /* Next position */
};

#define FTS5_LOOKAHEAD_EOF (((i64)1) << 62)

static int fts5LookaheadReaderNext(Fts5LookaheadReader *p){
 p->iPos = p->iLookahead;
 if( sqlite3Fts5PoslistNext64(p->a, p->n, &p->i, &p->iLookahead) ){
 p->iLookahead = FTS5_LOOKAHEAD_EOF;
 }
 return (p->iPos==FTS5_LOOKAHEAD_EOF);
}

static int fts5LookaheadReaderInit(
 const u8 *a, int n, /* Buffer to read position list from */
 Fts5LookaheadReader *p /* Iterator object to initialize */
){
 memset(p, 0, sizeof(Fts5LookaheadReader));
 p->a = a;
 p->n = n;
 fts5LookaheadReaderNext(p);
 return fts5LookaheadReaderNext(p);
}

typedef struct Fts5NearTrimmer Fts5NearTrimmer;
struct Fts5NearTrimmer {
 Fts5LookaheadReader reader; /* Input iterator */
 Fts5PoslistWriter writer; /* Writer context */
 Fts5Buffer *pOut; /* Output poslist */
};

/*
** The near-set object passed as the first argument contains more than
** one phrase. All phrases currently point to the same row. The
** Fts5ExprPhrase.poslist buffers are populated accordingly. This function
** tests if the current row contains instances of each phrase sufficiently
** close together to meet the NEAR constraint. Non-zero is returned if it
** does, or zero otherwise.
**
** If in/out parameter (*pRc) is set to other than SQLITE_OK when this
** function is called, it is a no-op. Or, if an error (e.g. SQLITE_NOMEM)
** occurs within this function (*pRc) is set accordingly before returning.
** The return value is undefined in both these cases.
**
** If no error occurs and non-zero (a match) is returned, the position-list
** of each phrase object is edited to contain only those entries that
** meet the constraint before returning.
*/
static int fts5ExprNearIsMatch(int *pRc, Fts5ExprNearset *pNear){
 Fts5NearTrimmer aStatic[4];
 Fts5NearTrimmer *a = aStatic;
 Fts5ExprPhrase **apPhrase = pNear->apPhrase;

 int i;
 int rc = *pRc;
 int bMatch;

 assert( pNear->nPhrase>1 );

 /* If the aStatic[] array is not large enough, allocate a large array
 ** using sqlite3_malloc(). This approach could be improved upon. */
 if( pNear->nPhrase>ArraySize(aStatic) ){
 sqlite3_int64 nByte = sizeof(Fts5NearTrimmer) * pNear->nPhrase;
 a = (Fts5NearTrimmer*)sqlite3Fts5MallocZero(&rc, nByte);
 }else{
 memset(aStatic, 0, sizeof(aStatic));
 }
 if( rc!=SQLITE_OK ){
 *pRc = rc;
 return 0;
 }

 /* Initialize a lookahead iterator for each phrase. After passing the
 ** buffer and buffer size to the lookaside-reader init function, zero
 ** the phrase poslist buffer. The new poslist for the phrase (containing
 ** the same entries as the original with some entries removed on account
 ** of the NEAR constraint) is written over the original even as it is
 ** being read. This is safe as the entries for the new poslist are a
 ** subset of the old, so it is not possible for data yet to be read to
 ** be overwritten. */
 for(i=0; i<pNear->nPhrase; i++){
 Fts5Buffer *pPoslist = &apPhrase[i]->poslist;
 fts5LookaheadReaderInit(pPoslist->p, pPoslist->n, &a[i].reader);
 pPoslist->n = 0;
 a[i].pOut = pPoslist;
 }

 while( 1 ){
 int iAdv;
 i64 iMin;
 i64 iMax;

 /* This block advances the phrase iterators until they point to a set of
 ** entries that together comprise a match. */
 iMax = a[0].reader.iPos;
 do {
 bMatch = 1;
 for(i=0; i<pNear->nPhrase; i++){
 Fts5LookaheadReader *pPos = &a[i].reader;
 iMin = iMax - pNear->apPhrase[i]->nTerm - pNear->nNear;
 if( pPos->iPos<iMin || pPos->iPos>iMax ){
 bMatch = 0;
 while( pPos->iPos<iMin ){
 if( fts5LookaheadReaderNext(pPos) ) goto ismatch_out;
 }
 if( pPos->iPos>iMax ) iMax = pPos->iPos;
 }
 }
 }while( bMatch==0 );

 /* Add an entry to each output position list */
 for(i=0; i<pNear->nPhrase; i++){
 i64 iPos = a[i].reader.iPos;
 Fts5PoslistWriter *pWriter = &a[i].writer;
 if( a[i].pOut->n==0 || iPos!=pWriter->iPrev ){
 sqlite3Fts5PoslistWriterAppend(a[i].pOut, pWriter, iPos);
 }
 }

 iAdv = 0;
 iMin = a[0].reader.iLookahead;
 for(i=0; i<pNear->nPhrase; i++){
 if( a[i].reader.iLookahead < iMin ){
 iMin = a[i].reader.iLookahead;
 iAdv = i;
 }
 }
 if( fts5LookaheadReaderNext(&a[iAdv].reader) ) goto ismatch_out;
 }

 ismatch_out: {
 int bRet = a[0].pOut->n>0;
 *pRc = rc;
 if( a!=aStatic ) sqlite3_free(a);
 return bRet;
 }
}

/*
** Advance iterator pIter until it points to a value equal to or laster
** than the initial value of *piLast. If this means the iterator points
** to a value laster than *piLast, update *piLast to the new lastest value.
**
** If the iterator reaches EOF, set *pbEof to true before returning. If
** an error occurs, set *pRc to an error code. If either *pbEof or *pRc
** are set, return a non-zero value. Otherwise, return zero.
*/
static int fts5ExprAdvanceto(
 Fts5IndexIter *pIter, /* Iterator to advance */
 int bDesc, /* True if iterator is "rowid DESC" */
 i64 *piLast, /* IN/OUT: Lastest rowid seen so far */
 int *pRc, /* OUT: Error code */
 int *pbEof /* OUT: Set to true if EOF */
){
 i64 iLast = *piLast;
 i64 iRowid;

 iRowid = pIter->iRowid;
 if( (bDesc==0 && iLast>iRowid) || (bDesc && iLast<iRowid) ){
 int rc = sqlite3Fts5IterNextFrom(pIter, iLast);
 if( rc || sqlite3Fts5IterEof(pIter) ){
 *pRc = rc;
 *pbEof = 1;
 return 1;
 }
 iRowid = pIter->iRowid;
 assert( (bDesc==0 && iRowid>=iLast) || (bDesc==1 && iRowid<=iLast) );
 }
 *piLast = iRowid;

 return 0;
}

static int fts5ExprSynonymAdvanceto(
 Fts5ExprTerm *pTerm, /* Term iterator to advance */
 int bDesc, /* True if iterator is "rowid DESC" */
 i64 *piLast, /* IN/OUT: Lastest rowid seen so far */
 int *pRc /* OUT: Error code */
){
 int rc = SQLITE_OK;
 i64 iLast = *piLast;
 Fts5ExprTerm *p;
 int bEof = 0;

 for(p=pTerm; rc==SQLITE_OK && p; p=p->pSynonym){
 if( sqlite3Fts5IterEof(p->pIter)==0 ){
 i64 iRowid = p->pIter->iRowid;
 if( (bDesc==0 && iLast>iRowid) || (bDesc && iLast<iRowid) ){
 rc = sqlite3Fts5IterNextFrom(p->pIter, iLast);
 }
 }
 }

 if( rc!=SQLITE_OK ){
 *pRc = rc;
 bEof = 1;
 }else{
 *piLast = fts5ExprSynonymRowid(pTerm, bDesc, &bEof);
 }
 return bEof;
}

static int fts5ExprNearTest(
 int *pRc,
 Fts5Expr *pExpr, /* Expression that pNear is a part of */
 Fts5ExprNode *pNode /* The "NEAR" node (FTS5_STRING) */
){
 Fts5ExprNearset *pNear = pNode->pNear;
 int rc = *pRc;

 if( pExpr->pConfig->eDetail!=FTS5_DETAIL_FULL ){
 Fts5ExprTerm *pTerm;
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[0];
 pPhrase->poslist.n = 0;
 for(pTerm=&pPhrase->aTerm[0]; pTerm; pTerm=pTerm->pSynonym){
 Fts5IndexIter *pIter = pTerm->pIter;
 if( sqlite3Fts5IterEof(pIter)==0 ){
 if( pIter->iRowid==pNode->iRowid && pIter->nData>0 ){
 pPhrase->poslist.n = 1;
 }
 }
 }
 return pPhrase->poslist.n;
 }else{
 int i;

 /* Check that each phrase in the nearset matches the current row.
 ** Populate the pPhrase->poslist buffers at the same time. If any
 ** phrase is not a match, break out of the loop early. */
 for(i=0; rc==SQLITE_OK && i<pNear->nPhrase; i++){
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[i];
 if( pPhrase->nTerm>1 || pPhrase->aTerm[0].pSynonym
 || pNear->pColset || pPhrase->aTerm[0].bFirst
 ){
 int bMatch = 0;
 rc = fts5ExprPhraseIsMatch(pNode, pPhrase, &bMatch);
 if( bMatch==0 ) break;
 }else{
 Fts5IndexIter *pIter = pPhrase->aTerm[0].pIter;
 fts5BufferSet(&rc, &pPhrase->poslist, pIter->nData, pIter->pData);
 }
 }

 *pRc = rc;
 if( i==pNear->nPhrase && (i==1 || fts5ExprNearIsMatch(pRc, pNear)) ){
 return 1;
 }
 return 0;
 }
}

/*
** Initialize all term iterators in the pNear object. If any term is found
** to match no documents at all, return immediately without initializing any
** further iterators.
**
** If an error occurs, return an SQLite error code. Otherwise, return
** SQLITE_OK. It is not considered an error if some term matches zero
** documents.
*/
static int fts5ExprNearInitAll(
 Fts5Expr *pExpr,
 Fts5ExprNode *pNode
){
 Fts5ExprNearset *pNear = pNode->pNear;
 int i;

 assert( pNode->bNomatch==0 );
 for(i=0; i<pNear->nPhrase; i++){
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[i];
 if( pPhrase->nTerm==0 ){
 pNode->bEof = 1;
 return SQLITE_OK;
 }else{
 int j;
 for(j=0; j<pPhrase->nTerm; j++){
 Fts5ExprTerm *pTerm = &pPhrase->aTerm[j];
 Fts5ExprTerm *p;
 int bHit = 0;

 for(p=pTerm; p; p=p->pSynonym){
 int rc;
 if( p->pIter ){
 sqlite3Fts5IterClose(p->pIter);
 p->pIter = 0;
 }
 rc = sqlite3Fts5IndexQuery(
 pExpr->pIndex, p->pTerm, p->nQueryTerm,
 (pTerm->bPrefix ? FTS5INDEX_QUERY_PREFIX : 0) |
 (pExpr->bDesc ? FTS5INDEX_QUERY_DESC : 0),
 pNear->pColset,
 &p->pIter
 );
 assert( (rc==SQLITE_OK)==(p->pIter!=0) );
 if( rc!=SQLITE_OK ) return rc;
 if( 0==sqlite3Fts5IterEof(p->pIter) ){
 bHit = 1;
 }
 }

 if( bHit==0 ){
 pNode->bEof = 1;
 return SQLITE_OK;
 }
 }
 }
 }

 pNode->bEof = 0;
 return SQLITE_OK;
}

/*
** If pExpr is an ASC iterator, this function returns a value with the
** same sign as:
**
** (iLhs - iRhs)
**
** Otherwise, if this is a DESC iterator, the opposite is returned:
**
** (iRhs - iLhs)
*/
static int fts5RowidCmp(
 Fts5Expr *pExpr,
 i64 iLhs,
 i64 iRhs
){
 assert( pExpr->bDesc==0 || pExpr->bDesc==1 );
 if( pExpr->bDesc==0 ){
 if( iLhs<iRhs ) return -1;
 return (iLhs > iRhs);
 }else{
 if( iLhs>iRhs ) return -1;
 return (iLhs < iRhs);
 }
}

static void fts5ExprSetEof(Fts5ExprNode *pNode){
 int i;
 pNode->bEof = 1;
 pNode->bNomatch = 0;
 for(i=0; i<pNode->nChild; i++){
 fts5ExprSetEof(pNode->apChild[i]);
 }
}

static void fts5ExprNodeZeroPoslist(Fts5ExprNode *pNode){
 if( pNode->eType==FTS5_STRING || pNode->eType==FTS5_TERM ){
 Fts5ExprNearset *pNear = pNode->pNear;
 int i;
 for(i=0; i<pNear->nPhrase; i++){
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[i];
 pPhrase->poslist.n = 0;
 }
 }else{
 int i;
 for(i=0; i<pNode->nChild; i++){
 fts5ExprNodeZeroPoslist(pNode->apChild[i]);
 }
 }
}

/*
** Compare the values currently indicated by the two nodes as follows:
**
** res = (*p1) - (*p2)
**
** Nodes that point to values that come later in the iteration order are
** considered to be larger. Nodes at EOF are the largest of all.
**
** This means that if the iteration order is ASC, then numerically larger
** rowids are considered larger. Or if it is the default DESC, numerically
** smaller rowids are larger.
*/
static int fts5NodeCompare(
 Fts5Expr *pExpr,
 Fts5ExprNode *p1,
 Fts5ExprNode *p2
){
 if( p2->bEof ) return -1;
 if( p1->bEof ) return +1;
 return fts5RowidCmp(pExpr, p1->iRowid, p2->iRowid);
}

/*
** All individual term iterators in pNear are guaranteed to be valid when
** this function is called. This function checks if all term iterators
** point to the same rowid, and if not, advances them until they do.
** If an EOF is reached before this happens, *pbEof is set to true before
** returning.
**
** SQLITE_OK is returned if an error occurs, or an SQLite error code
** otherwise. It is not considered an error code if an iterator reaches
** EOF.
*/
static int fts5ExprNodeTest_STRING(
 Fts5Expr *pExpr, /* Expression pPhrase belongs to */
 Fts5ExprNode *pNode
){
 Fts5ExprNearset *pNear = pNode->pNear;
 Fts5ExprPhrase *pLeft = pNear->apPhrase[0];
 int rc = SQLITE_OK;
 i64 iLast; /* Lastest rowid any iterator points to */
 int i, j; /* Phrase and token index, respectively */
 int bMatch; /* True if all terms are at the same rowid */
 const int bDesc = pExpr->bDesc;

 /* Check that this node should not be FTS5_TERM */
 assert( pNear->nPhrase>1
 || pNear->apPhrase[0]->nTerm>1
 || pNear->apPhrase[0]->aTerm[0].pSynonym
 || pNear->apPhrase[0]->aTerm[0].bFirst
 );

 /* Initialize iLast, the "lastest" rowid any iterator points to. If the
 ** iterator skips through rowids in the default ascending order, this means
 ** the maximum rowid. Or, if the iterator is "ORDER BY rowid DESC", then it
 ** means the minimum rowid. */
 if( pLeft->aTerm[0].pSynonym ){
 iLast = fts5ExprSynonymRowid(&pLeft->aTerm[0], bDesc, 0);
 }else{
 iLast = pLeft->aTerm[0].pIter->iRowid;
 }

 do {
 bMatch = 1;
 for(i=0; i<pNear->nPhrase; i++){
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[i];
 for(j=0; j<pPhrase->nTerm; j++){
 Fts5ExprTerm *pTerm = &pPhrase->aTerm[j];
 if( pTerm->pSynonym ){
 i64 iRowid = fts5ExprSynonymRowid(pTerm, bDesc, 0);
 if( iRowid==iLast ) continue;
 bMatch = 0;
 if( fts5ExprSynonymAdvanceto(pTerm, bDesc, &iLast, &rc) ){
 pNode->bNomatch = 0;
 pNode->bEof = 1;
 return rc;
 }
 }else{
 Fts5IndexIter *pIter = pPhrase->aTerm[j].pIter;
 if( pIter->iRowid==iLast ) continue;
 bMatch = 0;
 if( fts5ExprAdvanceto(pIter, bDesc, &iLast, &rc, &pNode->bEof) ){
 return rc;
 }
 }
 }
 }
 }while( bMatch==0 );

 pNode->iRowid = iLast;
 pNode->bNomatch = ((0==fts5ExprNearTest(&rc, pExpr, pNode)) && rc==SQLITE_OK);
 assert( pNode->bEof==0 || pNode->bNomatch==0 );

 return rc;
}

/*
** Advance the first term iterator in the first phrase of pNear. Set output
** variable *pbEof to true if it reaches EOF or if an error occurs.
**
** Return SQLITE_OK if successful, or an SQLite error code if an error
** occurs.
*/
static int fts5ExprNodeNext_STRING(
 Fts5Expr *pExpr, /* Expression pPhrase belongs to */
 Fts5ExprNode *pNode, /* FTS5_STRING or FTS5_TERM node */
 int bFromValid,
 i64 iFrom
){
 Fts5ExprTerm *pTerm = &pNode->pNear->apPhrase[0]->aTerm[0];
 int rc = SQLITE_OK;

 pNode->bNomatch = 0;
 if( pTerm->pSynonym ){
 int bEof = 1;
 Fts5ExprTerm *p;

 /* Find the firstest rowid any synonym points to. */
 i64 iRowid = fts5ExprSynonymRowid(pTerm, pExpr->bDesc, 0);

 /* Advance each iterator that currently points to iRowid. Or, if iFrom
 ** is valid - each iterator that points to a rowid before iFrom. */
 for(p=pTerm; p; p=p->pSynonym){
 if( sqlite3Fts5IterEof(p->pIter)==0 ){
 i64 ii = p->pIter->iRowid;
 if( ii==iRowid
 || (bFromValid && ii!=iFrom && (ii>iFrom)==pExpr->bDesc)
 ){
 if( bFromValid ){
 rc = sqlite3Fts5IterNextFrom(p->pIter, iFrom);
 }else{
 rc = sqlite3Fts5IterNext(p->pIter);
 }
 if( rc!=SQLITE_OK ) break;
 if( sqlite3Fts5IterEof(p->pIter)==0 ){
 bEof = 0;
 }
 }else{
 bEof = 0;
 }
 }
 }

 /* Set the EOF flag if either all synonym iterators are at EOF or an
 ** error has occurred. */
 pNode->bEof = (rc || bEof);
 }else{
 Fts5IndexIter *pIter = pTerm->pIter;

 assert( Fts5NodeIsString(pNode) );
 if( bFromValid ){
 rc = sqlite3Fts5IterNextFrom(pIter, iFrom);
 }else{
 rc = sqlite3Fts5IterNext(pIter);
 }

 pNode->bEof = (rc || sqlite3Fts5IterEof(pIter));
 }

 if( pNode->bEof==0 ){
 assert( rc==SQLITE_OK );
 rc = fts5ExprNodeTest_STRING(pExpr, pNode);
 }

 return rc;
}

static int fts5ExprNodeTest_TERM(
 Fts5Expr *pExpr, /* Expression that pNear is a part of */
 Fts5ExprNode *pNode /* The "NEAR" node (FTS5_TERM) */
){
 /* As this "NEAR" object is actually a single phrase that consists
 ** of a single term only, grab pointers into the poslist managed by the
 ** fts5_index.c iterator object. This is much faster than synthesizing
 ** a new poslist the way we have to for more complicated phrase or NEAR
 ** expressions. */
 Fts5ExprPhrase *pPhrase = pNode->pNear->apPhrase[0];
 Fts5IndexIter *pIter = pPhrase->aTerm[0].pIter;

 assert( pNode->eType==FTS5_TERM );
 assert( pNode->pNear->nPhrase==1 && pPhrase->nTerm==1 );
 assert( pPhrase->aTerm[0].pSynonym==0 );

 pPhrase->poslist.n = pIter->nData;
 if( pExpr->pConfig->eDetail==FTS5_DETAIL_FULL ){
 pPhrase->poslist.p = (u8*)pIter->pData;
 }
 pNode->iRowid = pIter->iRowid;
 pNode->bNomatch = (pPhrase->poslist.n==0);
 return SQLITE_OK;
}

/*
** xNext() method for a node of type FTS5_TERM.
*/
static int fts5ExprNodeNext_TERM(
 Fts5Expr *pExpr,
 Fts5ExprNode *pNode,
 int bFromValid,
 i64 iFrom
){
 int rc;
 Fts5IndexIter *pIter = pNode->pNear->apPhrase[0]->aTerm[0].pIter;

 assert( pNode->bEof==0 );
 if( bFromValid ){
 rc = sqlite3Fts5IterNextFrom(pIter, iFrom);
 }else{
 rc = sqlite3Fts5IterNext(pIter);
 }
 if( rc==SQLITE_OK && sqlite3Fts5IterEof(pIter)==0 ){
 rc = fts5ExprNodeTest_TERM(pExpr, pNode);
 }else{
 pNode->bEof = 1;
 pNode->bNomatch = 0;
 }
 return rc;
}

static void fts5ExprNodeTest_OR(
 Fts5Expr *pExpr, /* Expression of which pNode is a part */
 Fts5ExprNode *pNode /* Expression node to test */
){
 Fts5ExprNode *pNext = pNode->apChild[0];
 int i;

 for(i=1; i<pNode->nChild; i++){
 Fts5ExprNode *pChild = pNode->apChild[i];
 int cmp = fts5NodeCompare(pExpr, pNext, pChild);
 if( cmp>0 || (cmp==0 && pChild->bNomatch==0) ){
 pNext = pChild;
 }
 }
 pNode->iRowid = pNext->iRowid;
 pNode->bEof = pNext->bEof;
 pNode->bNomatch = pNext->bNomatch;
}

static int fts5ExprNodeNext_OR(
 Fts5Expr *pExpr,
 Fts5ExprNode *pNode,
 int bFromValid,
 i64 iFrom
){
 int i;
 i64 iLast = pNode->iRowid;

 for(i=0; i<pNode->nChild; i++){
 Fts5ExprNode *p1 = pNode->apChild[i];
 assert( p1->bEof || fts5RowidCmp(pExpr, p1->iRowid, iLast)>=0 );
 if( p1->bEof==0 ){
 if( (p1->iRowid==iLast)
 || (bFromValid && fts5RowidCmp(pExpr, p1->iRowid, iFrom)<0)
 ){
 int rc = fts5ExprNodeNext(pExpr, p1, bFromValid, iFrom);
 if( rc!=SQLITE_OK ){
 pNode->bNomatch = 0;
 return rc;
 }
 }
 }
 }

 fts5ExprNodeTest_OR(pExpr, pNode);
 return SQLITE_OK;
}

/*
** Argument pNode is an FTS5_AND node.
*/
static int fts5ExprNodeTest_AND(
 Fts5Expr *pExpr, /* Expression pPhrase belongs to */
 Fts5ExprNode *pAnd /* FTS5_AND node to advance */
){
 int iChild;
 i64 iLast = pAnd->iRowid;
 int rc = SQLITE_OK;
 int bMatch;

 assert( pAnd->bEof==0 );
 do {
 pAnd->bNomatch = 0;
 bMatch = 1;
 for(iChild=0; iChild<pAnd->nChild; iChild++){
 Fts5ExprNode *pChild = pAnd->apChild[iChild];
 int cmp = fts5RowidCmp(pExpr, iLast, pChild->iRowid);
 if( cmp>0 ){
 /* Advance pChild until it points to iLast or laster */
 rc = fts5ExprNodeNext(pExpr, pChild, 1, iLast);
 if( rc!=SQLITE_OK ){
 pAnd->bNomatch = 0;
 return rc;
 }
 }

 /* If the child node is now at EOF, so is the parent AND node. Otherwise,
 ** the child node is guaranteed to have advanced at least as far as
 ** rowid iLast. So if it is not at exactly iLast, pChild->iRowid is the
 ** new lastest rowid seen so far. */
 assert( pChild->bEof || fts5RowidCmp(pExpr, iLast, pChild->iRowid)<=0 );
 if( pChild->bEof ){
 fts5ExprSetEof(pAnd);
 bMatch = 1;
 break;
 }else if( iLast!=pChild->iRowid ){
 bMatch = 0;
 iLast = pChild->iRowid;
 }

 if( pChild->bNomatch ){
 pAnd->bNomatch = 1;
 }
 }
 }while( bMatch==0 );

 if( pAnd->bNomatch && pAnd!=pExpr->pRoot ){
 fts5ExprNodeZeroPoslist(pAnd);
 }
 pAnd->iRowid = iLast;
 return SQLITE_OK;
}

static int fts5ExprNodeNext_AND(
 Fts5Expr *pExpr,
 Fts5ExprNode *pNode,
 int bFromValid,
 i64 iFrom
){
 int rc = fts5ExprNodeNext(pExpr, pNode->apChild[0], bFromValid, iFrom);
 if( rc==SQLITE_OK ){
 rc = fts5ExprNodeTest_AND(pExpr, pNode);
 }else{
 pNode->bNomatch = 0;
 }
 return rc;
}

static int fts5ExprNodeTest_NOT(
 Fts5Expr *pExpr, /* Expression pPhrase belongs to */
 Fts5ExprNode *pNode /* FTS5_NOT node to advance */
){
 int rc = SQLITE_OK;
 Fts5ExprNode *p1 = pNode->apChild[0];
 Fts5ExprNode *p2 = pNode->apChild[1];
 assert( pNode->nChild==2 );

 while( rc==SQLITE_OK && p1->bEof==0 ){
 int cmp = fts5NodeCompare(pExpr, p1, p2);
 if( cmp>0 ){
 rc = fts5ExprNodeNext(pExpr, p2, 1, p1->iRowid);
 cmp = fts5NodeCompare(pExpr, p1, p2);
 }
 assert( rc!=SQLITE_OK || cmp<=0 );
 if( cmp || p2->bNomatch ) break;
 rc = fts5ExprNodeNext(pExpr, p1, 0, 0);
 }
 pNode->bEof = p1->bEof;
 pNode->bNomatch = p1->bNomatch;
 pNode->iRowid = p1->iRowid;
 if( p1->bEof ){
 fts5ExprNodeZeroPoslist(p2);
 }
 return rc;
}

static int fts5ExprNodeNext_NOT(
 Fts5Expr *pExpr,
 Fts5ExprNode *pNode,
 int bFromValid,
 i64 iFrom
){
 int rc = fts5ExprNodeNext(pExpr, pNode->apChild[0], bFromValid, iFrom);
 if( rc==SQLITE_OK ){
 rc = fts5ExprNodeTest_NOT(pExpr, pNode);
 }
 if( rc!=SQLITE_OK ){
 pNode->bNomatch = 0;
 }
 return rc;
}

/*
** If pNode currently points to a match, this function returns SQLITE_OK
** without modifying it. Otherwise, pNode is advanced until it does point
** to a match or EOF is reached.
*/
static int fts5ExprNodeTest(
 Fts5Expr *pExpr, /* Expression of which pNode is a part */
 Fts5ExprNode *pNode /* Expression node to test */
){
 int rc = SQLITE_OK;
 if( pNode->bEof==0 ){
 switch( pNode->eType ){

 case FTS5_STRING: {
 rc = fts5ExprNodeTest_STRING(pExpr, pNode);
 break;
 }

 case FTS5_TERM: {
 rc = fts5ExprNodeTest_TERM(pExpr, pNode);
 break;
 }

 case FTS5_AND: {
 rc = fts5ExprNodeTest_AND(pExpr, pNode);
 break;
 }

 case FTS5_OR: {
 fts5ExprNodeTest_OR(pExpr, pNode);
 break;
 }

 default: assert( pNode->eType==FTS5_NOT ); {
 rc = fts5ExprNodeTest_NOT(pExpr, pNode);
 break;
 }
 }
 }
 return rc;
}

/*
** Set node pNode, which is part of expression pExpr, to point to the first
** match. If there are no matches, set the Node.bEof flag to indicate EOF.
**
** Return an SQLite error code if an error occurs, or SQLITE_OK otherwise.
** It is not an error if there are no matches.
*/
static int fts5ExprNodeFirst(Fts5Expr *pExpr, Fts5ExprNode *pNode){
 int rc = SQLITE_OK;
 pNode->bEof = 0;
 pNode->bNomatch = 0;

 if( Fts5NodeIsString(pNode) ){
 /* Initialize all term iterators in the NEAR object. */
 rc = fts5ExprNearInitAll(pExpr, pNode);
 }else if( pNode->xNext==0 ){
 pNode->bEof = 1;
 }else{
 int i;
 int nEof = 0;
 for(i=0; i<pNode->nChild && rc==SQLITE_OK; i++){
 Fts5ExprNode *pChild = pNode->apChild[i];
 rc = fts5ExprNodeFirst(pExpr, pNode->apChild[i]);
 assert( pChild->bEof==0 || pChild->bEof==1 );
 nEof += pChild->bEof;
 }
 pNode->iRowid = pNode->apChild[0]->iRowid;

 switch( pNode->eType ){
 case FTS5_AND:
 if( nEof>0 ) fts5ExprSetEof(pNode);
 break;

 case FTS5_OR:
 if( pNode->nChild==nEof ) fts5ExprSetEof(pNode);
 break;

 default:
 assert( pNode->eType==FTS5_NOT );
 pNode->bEof = pNode->apChild[0]->bEof;
 break;
 }
 }

 if( rc==SQLITE_OK ){
 rc = fts5ExprNodeTest(pExpr, pNode);
 }
 return rc;
}

/*
** Begin iterating through the set of documents in index pIdx matched by
** the MATCH expression passed as the first argument. If the "bDesc"
** parameter is passed a non-zero value, iteration is in descending rowid
** order. Or, if it is zero, in ascending order.
**
** If iterating in ascending rowid order (bDesc==0), the first document
** visited is that with the smallest rowid that is larger than or equal
** to parameter iFirst. Or, if iterating in ascending order (bDesc==1),
** then the first document visited must have a rowid smaller than or
** equal to iFirst.
**
** Return SQLITE_OK if successful, or an SQLite error code otherwise. It
** is not considered an error if the query does not match any documents.
*/
static int sqlite3Fts5ExprFirst(Fts5Expr *p, Fts5Index *pIdx, i64 iFirst, int bDesc){
 Fts5ExprNode *pRoot = p->pRoot;
 int rc; /* Return code */

 p->pIndex = pIdx;
 p->bDesc = bDesc;
 rc = fts5ExprNodeFirst(p, pRoot);

 /* If not at EOF but the current rowid occurs earlier than iFirst in
 ** the iteration order, move to document iFirst or later. */
 if( rc==SQLITE_OK
 && 0==pRoot->bEof
 && fts5RowidCmp(p, pRoot->iRowid, iFirst)<0
 ){
 rc = fts5ExprNodeNext(p, pRoot, 1, iFirst);
 }

 /* If the iterator is not at a real match, skip forward until it is. */
 while( pRoot->bNomatch && rc==SQLITE_OK ){
 assert( pRoot->bEof==0 );
 rc = fts5ExprNodeNext(p, pRoot, 0, 0);
 }
 return rc;
}

/*
** Move to the next document
**
** Return SQLITE_OK if successful, or an SQLite error code otherwise. It
** is not considered an error if the query does not match any documents.
*/
static int sqlite3Fts5ExprNext(Fts5Expr *p, i64 iLast){
 int rc;
 Fts5ExprNode *pRoot = p->pRoot;
 assert( pRoot->bEof==0 && pRoot->bNomatch==0 );
 do {
 rc = fts5ExprNodeNext(p, pRoot, 0, 0);
 assert( pRoot->bNomatch==0 || (rc==SQLITE_OK && pRoot->bEof==0) );
 }while( pRoot->bNomatch );
 if( fts5RowidCmp(p, pRoot->iRowid, iLast)>0 ){
 pRoot->bEof = 1;
 }
 return rc;
}

static int sqlite3Fts5ExprEof(Fts5Expr *p){
 return p->pRoot->bEof;
}

static i64 sqlite3Fts5ExprRowid(Fts5Expr *p){
 return p->pRoot->iRowid;
}

static int fts5ParseStringFromToken(Fts5Token *pToken, char **pz){
 int rc = SQLITE_OK;
 *pz = sqlite3Fts5Strndup(&rc, pToken->p, pToken->n);
 return rc;
}

/*
** Free the phrase object passed as the only argument.
*/
static void fts5ExprPhraseFree(Fts5ExprPhrase *pPhrase){
 if( pPhrase ){
 int i;
 for(i=0; i<pPhrase->nTerm; i++){
 Fts5ExprTerm *pSyn;
 Fts5ExprTerm *pNext;
 Fts5ExprTerm *pTerm = &pPhrase->aTerm[i];
 sqlite3_free(pTerm->pTerm);
 sqlite3Fts5IterClose(pTerm->pIter);
 for(pSyn=pTerm->pSynonym; pSyn; pSyn=pNext){
 pNext = pSyn->pSynonym;
 sqlite3Fts5IterClose(pSyn->pIter);
 fts5BufferFree((Fts5Buffer*)&pSyn[1]);
 sqlite3_free(pSyn);
 }
 }
 if( pPhrase->poslist.nSpace>0 ) fts5BufferFree(&pPhrase->poslist);
 sqlite3_free(pPhrase);
 }
}

/*
** Set the "bFirst" flag on the first token of the phrase passed as the
** only argument.
*/
static void sqlite3Fts5ParseSetCaret(Fts5ExprPhrase *pPhrase){
 if( pPhrase && pPhrase->nTerm ){
 pPhrase->aTerm[0].bFirst = 1;
 }
}

/*
** If argument pNear is NULL, then a new Fts5ExprNearset object is allocated
** and populated with pPhrase. Or, if pNear is not NULL, phrase pPhrase is
** appended to it and the results returned.
**
** If an OOM error occurs, both the pNear and pPhrase objects are freed and
** NULL returned.
*/
static Fts5ExprNearset *sqlite3Fts5ParseNearset(
 Fts5Parse *pParse, /* Parse context */
 Fts5ExprNearset *pNear, /* Existing nearset, or NULL */
 Fts5ExprPhrase *pPhrase /* Recently parsed phrase */
){
 const int SZALLOC = 8;
 Fts5ExprNearset *pRet = 0;

 if( pParse->rc==SQLITE_OK ){
 if( pNear==0 ){
 sqlite3_int64 nByte;
 nByte = sizeof(Fts5ExprNearset) + SZALLOC * sizeof(Fts5ExprPhrase*);
 pRet = sqlite3_malloc64(nByte);
 if( pRet==0 ){
 pParse->rc = SQLITE_NOMEM;
 }else{
 memset(pRet, 0, (size_t)nByte);
 }
 }else if( (pNear->nPhrase % SZALLOC)==0 ){
 int nNew = pNear->nPhrase + SZALLOC;
 sqlite3_int64 nByte;

 nByte = sizeof(Fts5ExprNearset) + nNew * sizeof(Fts5ExprPhrase*);
 pRet = (Fts5ExprNearset*)sqlite3_realloc64(pNear, nByte);
 if( pRet==0 ){
 pParse->rc = SQLITE_NOMEM;
 }
 }else{
 pRet = pNear;
 }
 }

 if( pRet==0 ){
 assert( pParse->rc!=SQLITE_OK );
 sqlite3Fts5ParseNearsetFree(pNear);
 sqlite3Fts5ParsePhraseFree(pPhrase);
 }else{
 if( pRet->nPhrase>0 ){
 Fts5ExprPhrase *pLast = pRet->apPhrase[pRet->nPhrase-1];
 assert( pParse!=0 );
 assert( pParse->apPhrase!=0 );
 assert( pParse->nPhrase>=2 );
 assert( pLast==pParse->apPhrase[pParse->nPhrase-2] );
 if( pPhrase->nTerm==0 ){
 fts5ExprPhraseFree(pPhrase);
 pRet->nPhrase--;
 pParse->nPhrase--;
 pPhrase = pLast;
 }else if( pLast->nTerm==0 ){
 fts5ExprPhraseFree(pLast);
 pParse->apPhrase[pParse->nPhrase-2] = pPhrase;
 pParse->nPhrase--;
 pRet->nPhrase--;
 }
 }
 pRet->apPhrase[pRet->nPhrase++] = pPhrase;
 }
 return pRet;
}

typedef struct TokenCtx TokenCtx;
struct TokenCtx {
 Fts5ExprPhrase *pPhrase;
 Fts5Config *pConfig;
 int rc;
};

/*
** Callback for tokenizing terms used by ParseTerm().
*/
static int fts5ParseTokenize(
 void *pContext, /* Pointer to Fts5InsertCtx object */
 int tflags, /* Mask of FTS5_TOKEN_* flags */
 const char *pToken, /* Buffer containing token */
 int nToken, /* Size of token in bytes */
 int iUnused1, /* Start offset of token */
 int iUnused2 /* End offset of token */
){
 int rc = SQLITE_OK;
 const int SZALLOC = 8;
 TokenCtx *pCtx = (TokenCtx*)pContext;
 Fts5ExprPhrase *pPhrase = pCtx->pPhrase;

 UNUSED_PARAM2(iUnused1, iUnused2);

 /* If an error has already occurred, this is a no-op */
 if( pCtx->rc!=SQLITE_OK ) return pCtx->rc;
 if( nToken>FTS5_MAX_TOKEN_SIZE ) nToken = FTS5_MAX_TOKEN_SIZE;

 if( pPhrase && pPhrase->nTerm>0 && (tflags & FTS5_TOKEN_COLOCATED) ){
 Fts5ExprTerm *pSyn;
 sqlite3_int64 nByte = sizeof(Fts5ExprTerm) + sizeof(Fts5Buffer) + nToken+1;
 pSyn = (Fts5ExprTerm*)sqlite3_malloc64(nByte);
 if( pSyn==0 ){
 rc = SQLITE_NOMEM;
 }else{
 memset(pSyn, 0, (size_t)nByte);
 pSyn->pTerm = ((char*)pSyn) + sizeof(Fts5ExprTerm) + sizeof(Fts5Buffer);
 pSyn->nFullTerm = pSyn->nQueryTerm = nToken;
 if( pCtx->pConfig->bTokendata ){
 pSyn->nQueryTerm = (int)strlen(pSyn->pTerm);
 }
 memcpy(pSyn->pTerm, pToken, nToken);
 pSyn->pSynonym = pPhrase->aTerm[pPhrase->nTerm-1].pSynonym;
 pPhrase->aTerm[pPhrase->nTerm-1].pSynonym = pSyn;
 }
 }else{
 Fts5ExprTerm *pTerm;
 if( pPhrase==0 || (pPhrase->nTerm % SZALLOC)==0 ){
 Fts5ExprPhrase *pNew;
 int nNew = SZALLOC + (pPhrase ? pPhrase->nTerm : 0);

 pNew = (Fts5ExprPhrase*)sqlite3_realloc64(pPhrase,
 sizeof(Fts5ExprPhrase) + sizeof(Fts5ExprTerm) * nNew
 );
 if( pNew==0 ){
 rc = SQLITE_NOMEM;
 }else{
 if( pPhrase==0 ) memset(pNew, 0, sizeof(Fts5ExprPhrase));
 pCtx->pPhrase = pPhrase = pNew;
 pNew->nTerm = nNew - SZALLOC;
 }
 }

 if( rc==SQLITE_OK ){
 pTerm = &pPhrase->aTerm[pPhrase->nTerm++];
 memset(pTerm, 0, sizeof(Fts5ExprTerm));
 pTerm->pTerm = sqlite3Fts5Strndup(&rc, pToken, nToken);
 pTerm->nFullTerm = pTerm->nQueryTerm = nToken;
 if( pCtx->pConfig->bTokendata && rc==SQLITE_OK ){
 pTerm->nQueryTerm = (int)strlen(pTerm->pTerm);
 }
 }
 }

 pCtx->rc = rc;
 return rc;
}

/*
** Free the phrase object passed as the only argument.
*/
static void sqlite3Fts5ParsePhraseFree(Fts5ExprPhrase *pPhrase){
 fts5ExprPhraseFree(pPhrase);
}

/*
** Free the phrase object passed as the second argument.
*/
static void sqlite3Fts5ParseNearsetFree(Fts5ExprNearset *pNear){
 if( pNear ){
 int i;
 for(i=0; i<pNear->nPhrase; i++){
 fts5ExprPhraseFree(pNear->apPhrase[i]);
 }
 sqlite3_free(pNear->pColset);
 sqlite3_free(pNear);
 }
}

static void sqlite3Fts5ParseFinished(Fts5Parse *pParse, Fts5ExprNode *p){
 assert( pParse->pExpr==0 );
 pParse->pExpr = p;
}

static int parseGrowPhraseArray(Fts5Parse *pParse){
 if( (pParse->nPhrase % 8)==0 ){
 sqlite3_int64 nByte = sizeof(Fts5ExprPhrase*) * (pParse->nPhrase + 8);
 Fts5ExprPhrase **apNew;
 apNew = (Fts5ExprPhrase**)sqlite3_realloc64(pParse->apPhrase, nByte);
 if( apNew==0 ){
 pParse->rc = SQLITE_NOMEM;
 return SQLITE_NOMEM;
 }
 pParse->apPhrase = apNew;
 }
 return SQLITE_OK;
}

/*
** This function is called by the parser to process a string token. The
** string may or may not be quoted. In any case it is tokenized and a
** phrase object consisting of all tokens returned.
*/
static Fts5ExprPhrase *sqlite3Fts5ParseTerm(
 Fts5Parse *pParse, /* Parse context */
 Fts5ExprPhrase *pAppend, /* Phrase to append to */
 Fts5Token *pToken, /* String to tokenize */
 int bPrefix /* True if there is a trailing "*" */
){
 Fts5Config *pConfig = pParse->pConfig;
 TokenCtx sCtx; /* Context object passed to callback */
 int rc; /* Tokenize return code */
 char *z = 0;

 memset(&sCtx, 0, sizeof(TokenCtx));
 sCtx.pPhrase = pAppend;
 sCtx.pConfig = pConfig;

 rc = fts5ParseStringFromToken(pToken, &z);
 if( rc==SQLITE_OK ){
 int flags = FTS5_TOKENIZE_QUERY | (bPrefix ? FTS5_TOKENIZE_PREFIX : 0);
 int n;
 sqlite3Fts5Dequote(z);
 n = (int)strlen(z);
 rc = sqlite3Fts5Tokenize(pConfig, flags, z, n, &sCtx, fts5ParseTokenize);
 }
 sqlite3_free(z);
 if( rc || (rc = sCtx.rc) ){
 pParse->rc = rc;
 fts5ExprPhraseFree(sCtx.pPhrase);
 sCtx.pPhrase = 0;
 }else{

 if( pAppend==0 ){
 if( parseGrowPhraseArray(pParse) ){
 fts5ExprPhraseFree(sCtx.pPhrase);
 return 0;
 }
 pParse->nPhrase++;
 }

 if( sCtx.pPhrase==0 ){
 /* This happens when parsing a token or quoted phrase that contains
 ** no token characters at all. (e.g ... MATCH '""'). */
 sCtx.pPhrase = sqlite3Fts5MallocZero(&pParse->rc, sizeof(Fts5ExprPhrase));
 }else if( sCtx.pPhrase->nTerm ){
 sCtx.pPhrase->aTerm[sCtx.pPhrase->nTerm-1].bPrefix = (u8)bPrefix;
 }
 assert( pParse->apPhrase!=0 );
 pParse->apPhrase[pParse->nPhrase-1] = sCtx.pPhrase;
 }

 return sCtx.pPhrase;
}

/*
** Create a new FTS5 expression by cloning phrase iPhrase of the
** expression passed as the second argument.
*/
static int sqlite3Fts5ExprClonePhrase(
 Fts5Expr *pExpr,
 int iPhrase,
 Fts5Expr **ppNew
){
 int rc = SQLITE_OK; /* Return code */
 Fts5ExprPhrase *pOrig = 0; /* The phrase extracted from pExpr */
 Fts5Expr *pNew = 0; /* Expression to return via *ppNew */
 TokenCtx sCtx = {0,0,0}; /* Context object for fts5ParseTokenize */
 if( !pExpr || iPhrase<0 || iPhrase>=pExpr->nPhrase ){
 rc = SQLITE_RANGE;
 }else{
 pOrig = pExpr->apExprPhrase[iPhrase];
 pNew = (Fts5Expr*)sqlite3Fts5MallocZero(&rc, sizeof(Fts5Expr));
 }
 if( rc==SQLITE_OK ){
 pNew->apExprPhrase = (Fts5ExprPhrase**)sqlite3Fts5MallocZero(&rc,
 sizeof(Fts5ExprPhrase*));
 }
 if( rc==SQLITE_OK ){
 pNew->pRoot = (Fts5ExprNode*)sqlite3Fts5MallocZero(&rc,
 sizeof(Fts5ExprNode));
 }
 if( rc==SQLITE_OK ){
 pNew->pRoot->pNear = (Fts5ExprNearset*)sqlite3Fts5MallocZero(&rc,
 sizeof(Fts5ExprNearset) + sizeof(Fts5ExprPhrase*));
 }
 if( rc==SQLITE_OK && ALWAYS(pOrig!=0) ){
 Fts5Colset *pColsetOrig = pOrig->pNode->pNear->pColset;
 if( pColsetOrig ){
 sqlite3_int64 nByte;
 Fts5Colset *pColset;
 nByte = sizeof(Fts5Colset) + (pColsetOrig->nCol-1) * sizeof(int);
 pColset = (Fts5Colset*)sqlite3Fts5MallocZero(&rc, nByte);
 if( pColset ){
 memcpy(pColset, pColsetOrig, (size_t)nByte);
 }
 pNew->pRoot->pNear->pColset = pColset;
 }
 }

 if( rc==SQLITE_OK ){
 if( pOrig->nTerm ){
 int i; /* Used to iterate through phrase terms */
 sCtx.pConfig = pExpr->pConfig;
 for(i=0; rc==SQLITE_OK && i<pOrig->nTerm; i++){
 int tflags = 0;
 Fts5ExprTerm *p;
 for(p=&pOrig->aTerm[i]; p && rc==SQLITE_OK; p=p->pSynonym){
 rc = fts5ParseTokenize((void*)&sCtx,tflags,p->pTerm,p->nFullTerm,0,0);
 tflags = FTS5_TOKEN_COLOCATED;
 }
 if( rc==SQLITE_OK ){
 sCtx.pPhrase->aTerm[i].bPrefix = pOrig->aTerm[i].bPrefix;
 sCtx.pPhrase->aTerm[i].bFirst = pOrig->aTerm[i].bFirst;
 }
 }
 }else{
 /* This happens when parsing a token or quoted phrase that contains
 ** no token characters at all. (e.g ... MATCH '""'). */
 sCtx.pPhrase = sqlite3Fts5MallocZero(&rc, sizeof(Fts5ExprPhrase));
 }
 }

 if( rc==SQLITE_OK && ALWAYS(sCtx.pPhrase) ){
 /* All the allocations succeeded. Put the expression object together. */
 pNew->pIndex = pExpr->pIndex;
 pNew->pConfig = pExpr->pConfig;
 pNew->nPhrase = 1;
 pNew->apExprPhrase[0] = sCtx.pPhrase;
 pNew->pRoot->pNear->apPhrase[0] = sCtx.pPhrase;
 pNew->pRoot->pNear->nPhrase = 1;
 sCtx.pPhrase->pNode = pNew->pRoot;

 if( pOrig->nTerm==1
 && pOrig->aTerm[0].pSynonym==0
 && pOrig->aTerm[0].bFirst==0
 ){
 pNew->pRoot->eType = FTS5_TERM;
 pNew->pRoot->xNext = fts5ExprNodeNext_TERM;
 }else{
 pNew->pRoot->eType = FTS5_STRING;
 pNew->pRoot->xNext = fts5ExprNodeNext_STRING;
 }
 }else{
 sqlite3Fts5ExprFree(pNew);
 fts5ExprPhraseFree(sCtx.pPhrase);
 pNew = 0;
 }

 *ppNew = pNew;
 return rc;
}

/*
** Token pTok has appeared in a MATCH expression where the NEAR operator
** is expected. If token pTok does not contain "NEAR", store an error
** in the pParse object.
*/
static void sqlite3Fts5ParseNear(Fts5Parse *pParse, Fts5Token *pTok){
 if( pTok->n!=4 || memcmp("NEAR", pTok->p, 4) ){
 sqlite3Fts5ParseError(
 pParse, "fts5: syntax error near \"%.*s\"", pTok->n, pTok->p
 );
 }
}

static void sqlite3Fts5ParseSetDistance(
 Fts5Parse *pParse,
 Fts5ExprNearset *pNear,
 Fts5Token *p
){
 if( pNear ){
 int nNear = 0;
 int i;
 if( p->n ){
 for(i=0; i<p->n; i++){
 char c = (char)p->p[i];
 if( c<'0' || c>'9' ){
 sqlite3Fts5ParseError(
 pParse, "expected integer, got \"%.*s\"", p->n, p->p
 );
 return;
 }
 nNear = nNear * 10 + (p->p[i] - '0');
 }
 }else{
 nNear = FTS5_DEFAULT_NEARDIST;
 }
 pNear->nNear = nNear;
 }
}

/*
** The second argument passed to this function may be NULL, or it may be
** an existing Fts5Colset object. This function returns a pointer to
** a new colset object containing the contents of (p) with new value column
** number iCol appended.
**
** If an OOM error occurs, store an error code in pParse and return NULL.
** The old colset object (if any) is not freed in this case.
*/
static Fts5Colset *fts5ParseColset(
 Fts5Parse *pParse, /* Store SQLITE_NOMEM here if required */
 Fts5Colset *p, /* Existing colset object */
 int iCol /* New column to add to colset object */
){
 int nCol = p ? p->nCol : 0; /* Num. columns already in colset object */
 Fts5Colset *pNew; /* New colset object to return */

 assert( pParse->rc==SQLITE_OK );
 assert( iCol>=0 && iCol<pParse->pConfig->nCol );

 pNew = sqlite3_realloc64(p, sizeof(Fts5Colset) + sizeof(int)*nCol);
 if( pNew==0 ){
 pParse->rc = SQLITE_NOMEM;
 }else{
 int *aiCol = pNew->aiCol;
 int i, j;
 for(i=0; i<nCol; i++){
 if( aiCol[i]==iCol ) return pNew;
 if( aiCol[i]>iCol ) break;
 }
 for(j=nCol; j>i; j--){
 aiCol[j] = aiCol[j-1];
 }
 aiCol[i] = iCol;
 pNew->nCol = nCol+1;

#ifndef NDEBUG
 /* Check that the array is in order and contains no duplicate entries. */
 for(i=1; i<pNew->nCol; i++) assert( pNew->aiCol[i]>pNew->aiCol[i-1] );
#endif
 }

 return pNew;
}

/*
** Allocate and return an Fts5Colset object specifying the inverse of
** the colset passed as the second argument. Free the colset passed
** as the second argument before returning.
*/
static Fts5Colset *sqlite3Fts5ParseColsetInvert(Fts5Parse *pParse, Fts5Colset *p){
 Fts5Colset *pRet;
 int nCol = pParse->pConfig->nCol;

 pRet = (Fts5Colset*)sqlite3Fts5MallocZero(&pParse->rc,
 sizeof(Fts5Colset) + sizeof(int)*nCol
 );
 if( pRet ){
 int i;
 int iOld = 0;
 for(i=0; i<nCol; i++){
 if( iOld>=p->nCol || p->aiCol[iOld]!=i ){
 pRet->aiCol[pRet->nCol++] = i;
 }else{
 iOld++;
 }
 }
 }

 sqlite3_free(p);
 return pRet;
}

static Fts5Colset *sqlite3Fts5ParseColset(
 Fts5Parse *pParse, /* Store SQLITE_NOMEM here if required */
 Fts5Colset *pColset, /* Existing colset object */
 Fts5Token *p
){
 Fts5Colset *pRet = 0;
 int iCol;
 char *z; /* Dequoted copy of token p */

 z = sqlite3Fts5Strndup(&pParse->rc, p->p, p->n);
 if( pParse->rc==SQLITE_OK ){
 Fts5Config *pConfig = pParse->pConfig;
 sqlite3Fts5Dequote(z);
 for(iCol=0; iCol<pConfig->nCol; iCol++){
 if( 0==sqlite3_stricmp(pConfig->azCol[iCol], z) ) break;
 }
 if( iCol==pConfig->nCol ){
 sqlite3Fts5ParseError(pParse, "no such column: %s", z);
 }else{
 pRet = fts5ParseColset(pParse, pColset, iCol);
 }
 sqlite3_free(z);
 }

 if( pRet==0 ){
 assert( pParse->rc!=SQLITE_OK );
 sqlite3_free(pColset);
 }

 return pRet;
}

/*
** If argument pOrig is NULL, or if (*pRc) is set to anything other than
** SQLITE_OK when this function is called, NULL is returned.
**
** Otherwise, a copy of (*pOrig) is made into memory obtained from
** sqlite3Fts5MallocZero() and a pointer to it returned. If the allocation
** fails, (*pRc) is set to SQLITE_NOMEM and NULL is returned.
*/
static Fts5Colset *fts5CloneColset(int *pRc, Fts5Colset *pOrig){
 Fts5Colset *pRet;
 if( pOrig ){
 sqlite3_int64 nByte = sizeof(Fts5Colset) + (pOrig->nCol-1) * sizeof(int);
 pRet = (Fts5Colset*)sqlite3Fts5MallocZero(pRc, nByte);
 if( pRet ){
 memcpy(pRet, pOrig, (size_t)nByte);
 }
 }else{
 pRet = 0;
 }
 return pRet;
}

/*
** Remove from colset pColset any columns that are not also in colset pMerge.
*/
static void fts5MergeColset(Fts5Colset *pColset, Fts5Colset *pMerge){
 int iIn = 0; /* Next input in pColset */
 int iMerge = 0; /* Next input in pMerge */
 int iOut = 0; /* Next output slot in pColset */

 while( iIn<pColset->nCol && iMerge<pMerge->nCol ){
 int iDiff = pColset->aiCol[iIn] - pMerge->aiCol[iMerge];
 if( iDiff==0 ){
 pColset->aiCol[iOut++] = pMerge->aiCol[iMerge];
 iMerge++;
 iIn++;
 }else if( iDiff>0 ){
 iMerge++;
 }else{
 iIn++;
 }
 }
 pColset->nCol = iOut;
}

/*
** Recursively apply colset pColset to expression node pNode and all of
** its decendents. If (*ppFree) is not NULL, it contains a spare copy
** of pColset. This function may use the spare copy and set (*ppFree) to
** zero, or it may create copies of pColset using fts5CloneColset().
*/
static void fts5ParseSetColset(
 Fts5Parse *pParse,
 Fts5ExprNode *pNode,
 Fts5Colset *pColset,
 Fts5Colset **ppFree
){
 if( pParse->rc==SQLITE_OK ){
 assert( pNode->eType==FTS5_TERM || pNode->eType==FTS5_STRING
 || pNode->eType==FTS5_AND || pNode->eType==FTS5_OR
 || pNode->eType==FTS5_NOT || pNode->eType==FTS5_EOF
 );
 if( pNode->eType==FTS5_STRING || pNode->eType==FTS5_TERM ){
 Fts5ExprNearset *pNear = pNode->pNear;
 if( pNear->pColset ){
 fts5MergeColset(pNear->pColset, pColset);
 if( pNear->pColset->nCol==0 ){
 pNode->eType = FTS5_EOF;
 pNode->xNext = 0;
 }
 }else if( *ppFree ){
 pNear->pColset = pColset;
 *ppFree = 0;
 }else{
 pNear->pColset = fts5CloneColset(&pParse->rc, pColset);
 }
 }else{
 int i;
 assert( pNode->eType!=FTS5_EOF || pNode->nChild==0 );
 for(i=0; i<pNode->nChild; i++){
 fts5ParseSetColset(pParse, pNode->apChild[i], pColset, ppFree);
 }
 }
 }
}

/*
** Apply colset pColset to expression node pExpr and all of its descendents.
*/
static void sqlite3Fts5ParseSetColset(
 Fts5Parse *pParse,
 Fts5ExprNode *pExpr,
 Fts5Colset *pColset
){
 Fts5Colset *pFree = pColset;
 if( pParse->pConfig->eDetail==FTS5_DETAIL_NONE ){
 sqlite3Fts5ParseError(pParse,
 "fts5: column queries are not supported (detail=none)"
 );
 }else{
 fts5ParseSetColset(pParse, pExpr, pColset, &pFree);
 }
 sqlite3_free(pFree);
}

static void fts5ExprAssignXNext(Fts5ExprNode *pNode){
 switch( pNode->eType ){
 case FTS5_STRING: {
 Fts5ExprNearset *pNear = pNode->pNear;
 if( pNear->nPhrase==1 && pNear->apPhrase[0]->nTerm==1
 && pNear->apPhrase[0]->aTerm[0].pSynonym==0
 && pNear->apPhrase[0]->aTerm[0].bFirst==0
 ){
 pNode->eType = FTS5_TERM;
 pNode->xNext = fts5ExprNodeNext_TERM;
 }else{
 pNode->xNext = fts5ExprNodeNext_STRING;
 }
 break;
 };

 case FTS5_OR: {
 pNode->xNext = fts5ExprNodeNext_OR;
 break;
 };

 case FTS5_AND: {
 pNode->xNext = fts5ExprNodeNext_AND;
 break;
 };

 default: assert( pNode->eType==FTS5_NOT ); {
 pNode->xNext = fts5ExprNodeNext_NOT;
 break;
 };
 }
}

/*
** Add pSub as a child of p.
*/
static void fts5ExprAddChildren(Fts5ExprNode *p, Fts5ExprNode *pSub){
 int ii = p->nChild;
 if( p->eType!=FTS5_NOT && pSub->eType==p->eType ){
 int nByte = sizeof(Fts5ExprNode*) * pSub->nChild;
 memcpy(&p->apChild[p->nChild], pSub->apChild, nByte);
 p->nChild += pSub->nChild;
 sqlite3_free(pSub);
 }else{
 p->apChild[p->nChild++] = pSub;
 }
 for( ; ii<p->nChild; ii++){
 p->iHeight = MAX(p->iHeight, p->apChild[ii]->iHeight + 1);
 }
}

/*
** This function is used when parsing LIKE or GLOB patterns against
** trigram indexes that specify either detail=column or detail=none.
** It converts a phrase:
**
** abc + def + ghi
**
** into an AND tree:
**
** abc AND def AND ghi
*/
static Fts5ExprNode *fts5ParsePhraseToAnd(
 Fts5Parse *pParse,
 Fts5ExprNearset *pNear
){
 int nTerm = pNear->apPhrase[0]->nTerm;
 int ii;
 int nByte;
 Fts5ExprNode *pRet;

 assert( pNear->nPhrase==1 );
 assert( pParse->bPhraseToAnd );

 nByte = sizeof(Fts5ExprNode) + nTerm*sizeof(Fts5ExprNode*);
 pRet = (Fts5ExprNode*)sqlite3Fts5MallocZero(&pParse->rc, nByte);
 if( pRet ){
 pRet->eType = FTS5_AND;
 pRet->nChild = nTerm;
 pRet->iHeight = 1;
 fts5ExprAssignXNext(pRet);
 pParse->nPhrase--;
 for(ii=0; ii<nTerm; ii++){
 Fts5ExprPhrase *pPhrase = (Fts5ExprPhrase*)sqlite3Fts5MallocZero(
 &pParse->rc, sizeof(Fts5ExprPhrase)
 );
 if( pPhrase ){
 if( parseGrowPhraseArray(pParse) ){
 fts5ExprPhraseFree(pPhrase);
 }else{
 Fts5ExprTerm *p = &pNear->apPhrase[0]->aTerm[ii];
 Fts5ExprTerm *pTo = &pPhrase->aTerm[0];
 pParse->apPhrase[pParse->nPhrase++] = pPhrase;
 pPhrase->nTerm = 1;
 pTo->pTerm = sqlite3Fts5Strndup(&pParse->rc, p->pTerm, p->nFullTerm);
 pTo->nQueryTerm = p->nQueryTerm;
 pTo->nFullTerm = p->nFullTerm;
 pRet->apChild[ii] = sqlite3Fts5ParseNode(pParse, FTS5_STRING,
 0, 0, sqlite3Fts5ParseNearset(pParse, 0, pPhrase)
 );
 }
 }
 }

 if( pParse->rc ){
 sqlite3Fts5ParseNodeFree(pRet);
 pRet = 0;
 }else{
 sqlite3Fts5ParseNearsetFree(pNear);
 }
 }

 return pRet;
}

/*
** Allocate and return a new expression object. If anything goes wrong (i.e.
** OOM error), leave an error code in pParse and return NULL.
*/
static Fts5ExprNode *sqlite3Fts5ParseNode(
 Fts5Parse *pParse, /* Parse context */
 int eType, /* FTS5_STRING, AND, OR or NOT */
 Fts5ExprNode *pLeft, /* Left hand child expression */
 Fts5ExprNode *pRight, /* Right hand child expression */
 Fts5ExprNearset *pNear /* For STRING expressions, the near cluster */
){
 Fts5ExprNode *pRet = 0;

 if( pParse->rc==SQLITE_OK ){
 int nChild = 0; /* Number of children of returned node */
 sqlite3_int64 nByte; /* Bytes of space to allocate for this node */

 assert( (eType!=FTS5_STRING && !pNear)
 || (eType==FTS5_STRING && !pLeft && !pRight)
 );
 if( eType==FTS5_STRING && pNear==0 ) return 0;
 if( eType!=FTS5_STRING && pLeft==0 ) return pRight;
 if( eType!=FTS5_STRING && pRight==0 ) return pLeft;

 if( eType==FTS5_STRING
 && pParse->bPhraseToAnd
 && pNear->apPhrase[0]->nTerm>1
 ){
 pRet = fts5ParsePhraseToAnd(pParse, pNear);
 }else{
 if( eType==FTS5_NOT ){
 nChild = 2;
 }else if( eType==FTS5_AND || eType==FTS5_OR ){
 nChild = 2;
 if( pLeft->eType==eType ) nChild += pLeft->nChild-1;
 if( pRight->eType==eType ) nChild += pRight->nChild-1;
 }

 nByte = sizeof(Fts5ExprNode) + sizeof(Fts5ExprNode*)*(nChild-1);
 pRet = (Fts5ExprNode*)sqlite3Fts5MallocZero(&pParse->rc, nByte);

 if( pRet ){
 pRet->eType = eType;
 pRet->pNear = pNear;
 fts5ExprAssignXNext(pRet);
 if( eType==FTS5_STRING ){
 int iPhrase;
 for(iPhrase=0; iPhrase<pNear->nPhrase; iPhrase++){
 pNear->apPhrase[iPhrase]->pNode = pRet;
 if( pNear->apPhrase[iPhrase]->nTerm==0 ){
 pRet->xNext = 0;
 pRet->eType = FTS5_EOF;
 }
 }

 if( pParse->pConfig->eDetail!=FTS5_DETAIL_FULL ){
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[0];
 if( pNear->nPhrase!=1
 || pPhrase->nTerm>1
 || (pPhrase->nTerm>0 && pPhrase->aTerm[0].bFirst)
 ){
 sqlite3Fts5ParseError(pParse,
 "fts5: %s queries are not supported (detail!=full)",
 pNear->nPhrase==1 ? "phrase": "NEAR"
 );
 sqlite3Fts5ParseNodeFree(pRet);
 pRet = 0;
 pNear = 0;
 assert( pLeft==0 && pRight==0 );
 }
 }
 }else{
 assert( pNear==0 );
 fts5ExprAddChildren(pRet, pLeft);
 fts5ExprAddChildren(pRet, pRight);
 pLeft = pRight = 0;
 if( pRet->iHeight>SQLITE_FTS5_MAX_EXPR_DEPTH ){
 sqlite3Fts5ParseError(pParse,
 "fts5 expression tree is too large (maximum depth %d)",
 SQLITE_FTS5_MAX_EXPR_DEPTH
 );
 sqlite3Fts5ParseNodeFree(pRet);
 pRet = 0;
 }
 }
 }
 }
 }

 if( pRet==0 ){
 assert( pParse->rc!=SQLITE_OK );
 sqlite3Fts5ParseNodeFree(pLeft);
 sqlite3Fts5ParseNodeFree(pRight);
 sqlite3Fts5ParseNearsetFree(pNear);
 }
 return pRet;
}

static Fts5ExprNode *sqlite3Fts5ParseImplicitAnd(
 Fts5Parse *pParse, /* Parse context */
 Fts5ExprNode *pLeft, /* Left hand child expression */
 Fts5ExprNode *pRight /* Right hand child expression */
){
 Fts5ExprNode *pRet = 0;
 Fts5ExprNode *pPrev;

 if( pParse->rc ){
 sqlite3Fts5ParseNodeFree(pLeft);
 sqlite3Fts5ParseNodeFree(pRight);
 }else{

 assert( pLeft->eType==FTS5_STRING
 || pLeft->eType==FTS5_TERM
 || pLeft->eType==FTS5_EOF
 || pLeft->eType==FTS5_AND
 );
 assert( pRight->eType==FTS5_STRING
 || pRight->eType==FTS5_TERM
 || pRight->eType==FTS5_EOF
 || (pRight->eType==FTS5_AND && pParse->bPhraseToAnd)
 );

 if( pLeft->eType==FTS5_AND ){
 pPrev = pLeft->apChild[pLeft->nChild-1];
 }else{
 pPrev = pLeft;
 }
 assert( pPrev->eType==FTS5_STRING
 || pPrev->eType==FTS5_TERM
 || pPrev->eType==FTS5_EOF
 );

 if( pRight->eType==FTS5_EOF ){
 assert( pParse->apPhrase!=0 );
 assert( pParse->nPhrase>0 );
 assert( pParse->apPhrase[pParse->nPhrase-1]==pRight->pNear->apPhrase[0] );
 sqlite3Fts5ParseNodeFree(pRight);
 pRet = pLeft;
 pParse->nPhrase--;
 }
 else if( pPrev->eType==FTS5_EOF ){
 Fts5ExprPhrase **ap;

 if( pPrev==pLeft ){
 pRet = pRight;
 }else{
 pLeft->apChild[pLeft->nChild-1] = pRight;
 pRet = pLeft;
 }

 ap = &pParse->apPhrase[pParse->nPhrase-1-pRight->pNear->nPhrase];
 assert( ap[0]==pPrev->pNear->apPhrase[0] );
 memmove(ap, &ap[1], sizeof(Fts5ExprPhrase*)*pRight->pNear->nPhrase);
 pParse->nPhrase--;

 sqlite3Fts5ParseNodeFree(pPrev);
 }
 else{
 pRet = sqlite3Fts5ParseNode(pParse, FTS5_AND, pLeft, pRight, 0);
 }
 }

 return pRet;
}

#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
static char *fts5ExprTermPrint(Fts5ExprTerm *pTerm){
 sqlite3_int64 nByte = 0;
 Fts5ExprTerm *p;
 char *zQuoted;

 /* Determine the maximum amount of space required. */
 for(p=pTerm; p; p=p->pSynonym){
 nByte += pTerm->nQueryTerm * 2 + 3 + 2;
 }
 zQuoted = sqlite3_malloc64(nByte);

 if( zQuoted ){
 int i = 0;
 for(p=pTerm; p; p=p->pSynonym){
 char *zIn = p->pTerm;
 char *zEnd = &zIn[p->nQueryTerm];
 zQuoted[i++] = '"';
 while( zIn<zEnd ){
 if( *zIn=='"' ) zQuoted[i++] = '"';
 zQuoted[i++] = *zIn++;
 }
 zQuoted[i++] = '"';
 if( p->pSynonym ) zQuoted[i++] = '|';
 }
 if( pTerm->bPrefix ){
 zQuoted[i++] = ' ';
 zQuoted[i++] = '*';
 }
 zQuoted[i++] = '\0';
 }
 return zQuoted;
}

static char *fts5PrintfAppend(char *zApp, const char *zFmt, ...){
 char *zNew;
 va_list ap;
 va_start(ap, zFmt);
 zNew = sqlite3_vmprintf(zFmt, ap);
 va_end(ap);
 if( zApp && zNew ){
 char *zNew2 = sqlite3_mprintf("%s%s", zApp, zNew);
 sqlite3_free(zNew);
 zNew = zNew2;
 }
 sqlite3_free(zApp);
 return zNew;
}

/*
** Compose a tcl-readable representation of expression pExpr. Return a
** pointer to a buffer containing that representation. It is the
** responsibility of the caller to at some point free the buffer using
** sqlite3_free().
*/
static char *fts5ExprPrintTcl(
 Fts5Config *pConfig,
 const char *zNearsetCmd,
 Fts5ExprNode *pExpr
){
 char *zRet = 0;
 if( pExpr->eType==FTS5_STRING || pExpr->eType==FTS5_TERM ){
 Fts5ExprNearset *pNear = pExpr->pNear;
 int i;
 int iTerm;

 zRet = fts5PrintfAppend(zRet, "%s ", zNearsetCmd);
 if( zRet==0 ) return 0;
 if( pNear->pColset ){
 int *aiCol = pNear->pColset->aiCol;
 int nCol = pNear->pColset->nCol;
 if( nCol==1 ){
 zRet = fts5PrintfAppend(zRet, "-col %d ", aiCol[0]);
 }else{
 zRet = fts5PrintfAppend(zRet, "-col {%d", aiCol[0]);
 for(i=1; i<pNear->pColset->nCol; i++){
 zRet = fts5PrintfAppend(zRet, " %d", aiCol[i]);
 }
 zRet = fts5PrintfAppend(zRet, "} ");
 }
 if( zRet==0 ) return 0;
 }

 if( pNear->nPhrase>1 ){
 zRet = fts5PrintfAppend(zRet, "-near %d ", pNear->nNear);
 if( zRet==0 ) return 0;
 }

 zRet = fts5PrintfAppend(zRet, "--");
 if( zRet==0 ) return 0;

 for(i=0; i<pNear->nPhrase; i++){
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[i];

 zRet = fts5PrintfAppend(zRet, " {");
 for(iTerm=0; zRet && iTerm<pPhrase->nTerm; iTerm++){
 Fts5ExprTerm *p = &pPhrase->aTerm[iTerm];
 zRet = fts5PrintfAppend(zRet, "%s%.*s", iTerm==0?"":" ",
 p->nQueryTerm, p->pTerm
 );
 if( pPhrase->aTerm[iTerm].bPrefix ){
 zRet = fts5PrintfAppend(zRet, "*");
 }
 }

 if( zRet ) zRet = fts5PrintfAppend(zRet, "}");
 if( zRet==0 ) return 0;
 }

 }else if( pExpr->eType==0 ){
 zRet = sqlite3_mprintf("{}");
 }else{
 char const *zOp = 0;
 int i;
 switch( pExpr->eType ){
 case FTS5_AND: zOp = "AND"; break;
 case FTS5_NOT: zOp = "NOT"; break;
 default:
 assert( pExpr->eType==FTS5_OR );
 zOp = "OR";
 break;
 }

 zRet = sqlite3_mprintf("%s", zOp);
 for(i=0; zRet && i<pExpr->nChild; i++){
 char *z = fts5ExprPrintTcl(pConfig, zNearsetCmd, pExpr->apChild[i]);
 if( !z ){
 sqlite3_free(zRet);
 zRet = 0;
 }else{
 zRet = fts5PrintfAppend(zRet, " [%z]", z);
 }
 }
 }

 return zRet;
}

static char *fts5ExprPrint(Fts5Config *pConfig, Fts5ExprNode *pExpr){
 char *zRet = 0;
 if( pExpr->eType==0 ){
 return sqlite3_mprintf("\"\"");
 }else
 if( pExpr->eType==FTS5_STRING || pExpr->eType==FTS5_TERM ){
 Fts5ExprNearset *pNear = pExpr->pNear;
 int i;
 int iTerm;

 if( pNear->pColset ){
 int ii;
 Fts5Colset *pColset = pNear->pColset;
 if( pColset->nCol>1 ) zRet = fts5PrintfAppend(zRet, "{");
 for(ii=0; ii<pColset->nCol; ii++){
 zRet = fts5PrintfAppend(zRet, "%s%s",
 pConfig->azCol[pColset->aiCol[ii]], ii==pColset->nCol-1 ? "" : " "
 );
 }
 if( zRet ){
 zRet = fts5PrintfAppend(zRet, "%s : ", pColset->nCol>1 ? "}" : "");
 }
 if( zRet==0 ) return 0;
 }

 if( pNear->nPhrase>1 ){
 zRet = fts5PrintfAppend(zRet, "NEAR(");
 if( zRet==0 ) return 0;
 }

 for(i=0; i<pNear->nPhrase; i++){
 Fts5ExprPhrase *pPhrase = pNear->apPhrase[i];
 if( i!=0 ){
 zRet = fts5PrintfAppend(zRet, " ");
 if( zRet==0 ) return 0;
 }
 for(iTerm=0; iTerm<pPhrase->nTerm; iTerm++){
 char *zTerm = fts5ExprTermPrint(&pPhrase->aTerm[iTerm]);
 if( zTerm ){
 zRet = fts5PrintfAppend(zRet, "%s%s", iTerm==0?"":" + ", zTerm);
 sqlite3_free(zTerm);
 }
 if( zTerm==0 || zRet==0 ){
 sqlite3_free(zRet);
 return 0;
 }
 }
 }

 if( pNear->nPhrase>1 ){
 zRet = fts5PrintfAppend(zRet, ", %d)", pNear->nNear);
 if( zRet==0 ) return 0;
 }

 }else{
 char const *zOp = 0;
 int i;

 switch( pExpr->eType ){
 case FTS5_AND: zOp = " AND "; break;
 case FTS5_NOT: zOp = " NOT "; break;
 default:
 assert( pExpr->eType==FTS5_OR );
 zOp = " OR ";
 break;
 }

 for(i=0; i<pExpr->nChild; i++){
 char *z = fts5ExprPrint(pConfig, pExpr->apChild[i]);
 if( z==0 ){
 sqlite3_free(zRet);
 zRet = 0;
 }else{
 int e = pExpr->apChild[i]->eType;
 int b = (e!=FTS5_STRING && e!=FTS5_TERM && e!=FTS5_EOF);
 zRet = fts5PrintfAppend(zRet, "%s%s%z%s",
 (i==0 ? "" : zOp),
 (b?"(":""), z, (b?")":"")
 );
 }
 if( zRet==0 ) break;
 }
 }

 return zRet;
}

/*
** The implementation of user-defined scalar functions fts5_expr() (bTcl==0)
** and fts5_expr_tcl() (bTcl!=0).
*/
static void fts5ExprFunction(
 sqlite3_context *pCtx, /* Function call context */
 int nArg, /* Number of args */
 sqlite3_value **apVal, /* Function arguments */
 int bTcl
){
 Fts5Global *pGlobal = (Fts5Global*)sqlite3_user_data(pCtx);
 sqlite3 *db = sqlite3_context_db_handle(pCtx);
 const char *zExpr = 0;
 char *zErr = 0;
 Fts5Expr *pExpr = 0;
 int rc;
 int i;

 const char **azConfig; /* Array of arguments for Fts5Config */
 const char *zNearsetCmd = "nearset";
 int nConfig; /* Size of azConfig[] */
 Fts5Config *pConfig = 0;
 int iArg = 1;

 if( nArg<1 ){
 zErr = sqlite3_mprintf("wrong number of arguments to function %s",
 bTcl ? "fts5_expr_tcl" : "fts5_expr"
 );
 sqlite3_result_error(pCtx, zErr, -1);
 sqlite3_free(zErr);
 return;
 }

 if( bTcl && nArg>1 ){
 zNearsetCmd = (const char*)sqlite3_value_text(apVal[1]);
 iArg = 2;
 }

 nConfig = 3 + (nArg-iArg);
 azConfig = (const char**)sqlite3_malloc64(sizeof(char*) * nConfig);
 if( azConfig==0 ){
 sqlite3_result_error_nomem(pCtx);
 return;
 }
 azConfig[0] = 0;
 azConfig[1] = "main";
 azConfig[2] = "tbl";
 for(i=3; iArg<nArg; iArg++){
 const char *z = (const char*)sqlite3_value_text(apVal[iArg]);
 azConfig[i++] = (z ? z : "");
 }

 zExpr = (const char*)sqlite3_value_text(apVal[0]);
 if( zExpr==0 ) zExpr = "";

 rc = sqlite3Fts5ConfigParse(pGlobal, db, nConfig, azConfig, &pConfig, &zErr);
 if( rc==SQLITE_OK ){
 rc = sqlite3Fts5ExprNew(pConfig, 0, pConfig->nCol, zExpr, &pExpr, &zErr);
 }
 if( rc==SQLITE_OK ){
 char *zText;
 if( pExpr->pRoot->xNext==0 ){
 zText = sqlite3_mprintf("");
 }else if( bTcl ){
 zText = fts5ExprPrintTcl(pConfig, zNearsetCmd, pExpr->pRoot);
 }else{
 zText = fts5ExprPrint(pConfig, pExpr->pRoot);
 }
 if( zText==0 ){
 rc = SQLITE_NOMEM;
 }else{
 sqlite3_result_text(pCtx, zText, -1, SQLITE_TRANSIENT);
 sqlite3_free(zText);
 }
 }

 if( rc!=SQLITE_OK ){
 if( zErr ){
 sqlite3_result_error(pCtx, zErr, -1);
 sqlite3_free(zErr);
 }else{
 sqlite3_result_error_code(pCtx, rc);
 }
 }
 sqlite3_free((void *)azConfig);
 sqlite3Fts5ConfigFree(pConfig);
 sqlite3Fts5ExprFree(pExpr);
}

static void fts5ExprFunctionHr(
 sqlite3_context *pCtx, /* Function call context */
 int nArg, /* Number of args */
 sqlite3_value **apVal /* Function arguments */
){
 fts5ExprFunction(pCtx, nArg, apVal, 0);
}
static void fts5ExprFunctionTcl(
 sqlite3_context *pCtx, /* Function call context */
 int nArg, /* Number of args */
 sqlite3_value **apVal /* Function arguments */
){
 fts5ExprFunction(pCtx, nArg, apVal, 1);
}

/*
** The implementation of an SQLite user-defined-function that accepts a
** single integer as an argument. If the integer is an alpha-numeric
** unicode code point, 1 is returned. Otherwise 0.
*/
static void fts5ExprIsAlnum(
 sqlite3_context *pCtx, /* Function call context */
 int nArg, /* Number of args */
 sqlite3_value **apVal /* Function arguments */
){
 int iCode;
 u8 aArr[32];
 if( nArg!=1 ){
 sqlite3_result_error(pCtx,
 "wrong number of arguments to function fts5_isalnum", -1
 );
 return;
 }
 memset(aArr, 0, sizeof(aArr));
 sqlite3Fts5UnicodeCatParse("L*", aArr);
 sqlite3Fts5UnicodeCatParse("N*", aArr);
 sqlite3Fts5UnicodeCatParse("Co", aArr);
 iCode = sqlite3_value_int(apVal[0]);
 sqlite3_result_int(pCtx, aArr[sqlite3Fts5UnicodeCategory((u32)iCode)]);
}

static void fts5ExprFold(
 sqlite3_context *pCtx, /* Function call context */
 int nArg, /* Number of args */
 sqlite3_value **apVal /* Function arguments */
){
 if( nArg!=1 && nArg!=2 ){
 sqlite3_result_error(pCtx,
 "wrong number of arguments to function fts5_fold", -1
 );
 }else{
 int iCode;
 int bRemoveDiacritics = 0;
 iCode = sqlite3_value_int(apVal[0]);
 if( nArg==2 ) bRemoveDiacritics = sqlite3_value_int(apVal[1]);
 sqlite3_result_int(pCtx, sqlite3Fts5UnicodeFold(iCode, bRemoveDiacritics));
 }
}
#endif /* if SQLITE_TEST || SQLITE_FTS5_DEBUG */

/*
** This is called during initialization to register the fts5_expr() scalar
** UDF with the SQLite handle passed as the only argument.
*/
static int sqlite3Fts5ExprInit(Fts5Global *pGlobal, sqlite3 *db){
#if defined(SQLITE_TEST) || defined(SQLITE_FTS5_DEBUG)
 struct Fts5ExprFunc {
 const char *z;
 void (*x)(sqlite3_context*,int,sqlite3_value**);
 } aFunc[] = {
 { "fts5_expr", fts5ExprFunctionHr },
 { "fts5_expr_tcl", fts5ExprFunctionTcl },
 { "fts5_isalnum", fts5ExprIsAlnum },
 { "fts5_fold", fts5ExprFold },
 };
 int i;
 int rc = SQLITE_OK;
 void *pCtx = (void*)pGlobal;

 for(i=0; rc==SQLITE_OK && i<ArraySize(aFunc); i++){
 struct Fts5ExprFunc *p = &aFunc[i];
 rc = sqlite3_create_function(db, p->z, -1, SQLITE_UTF8, pCtx, p->x, 0, 0);
 }
#else
 int rc = SQLITE_OK;
 UNUSED_PARAM2(pGlobal,db);
#endif

 /* Avoid warnings indicating that sqlite3Fts5ParserTrace() and
 ** sqlite3Fts5ParserFallback() are unused */
#ifndef NDEBUG
 (void)sqlite3Fts5ParserTrace;
#endif
 (void)sqlite3Fts5ParserFallback;

 return rc;
}

/*
** Return the number of phrases in expression pExpr.
*/
static int sqlite3Fts5ExprPhraseCount(Fts5Expr *pExpr){
 return (pExpr ? pExpr->nPhrase : 0);
}

/*
** Return the number of terms in the iPhrase'th phrase in pExpr.
*/
static int sqlite3Fts5ExprPhraseSize(Fts5Expr *pExpr, int iPhrase){
 if( iPhrase<0 || iPhrase>=pExpr->nPhrase ) return 0;
 return pExpr->apExprPhrase[iPhrase]->nTerm;
}

/*
** This function is used to access the current position list for phrase
** iPhrase.
*/
static int sqlite3Fts5ExprPoslist(Fts5Expr *pExpr, int iPhrase, const u8 **pa){
 int nRet;
 Fts5ExprPhrase *pPhrase = pExpr->apExprPhrase[iPhrase];
 Fts5ExprNode *pNode = pPhrase->pNode;
 if( pNode->bEof==0 && pNode->iRowid==pExpr->pRoot->iRowid ){
 *pa = pPhrase->poslist.p;
 nRet = pPhrase->poslist.n;
 }else{
 *pa = 0;
 nRet = 0;
 }
 return nRet;
}

struct Fts5PoslistPopulator {
 Fts5PoslistWriter writer;
 int bOk; /* True if ok to populate */
 int bMiss;
};

/*
** Clear the position lists associated with all phrases in the expression
** passed as the first argument. Argument bLive is true if the expression
** might be pointing to a real entry, otherwise it has just been reset.
**
** At present this function is only used for detail=col and detail=none
** fts5 tables. This implies that all phrases must be at most 1 token
** in size, as phrase matches are not supported without detail=full.
*/
static Fts5PoslistPopulator *sqlite3Fts5ExprClearPoslists(Fts5Expr *pExpr, int bLive){
 Fts5PoslistPopulator *pRet;
 pRet = sqlite3_malloc64(sizeof(Fts5PoslistPopulator)*pExpr->nPhrase);
 if( pRet ){
 int i;
 memset(pRet, 0, sizeof(Fts5PoslistPopulator)*pExpr->nPhrase);
 for(i=0; i<pExpr->nPhrase; i++){
 Fts5Buffer *pBuf = &pExpr->apExprPhrase[i]->poslist;
 Fts5ExprNode *pNode = pExpr->apExprPhrase[i]->pNode;
 assert( pExpr->apExprPhrase[i]->nTerm<=1 );
 if( bLive &&
 (pBuf->n==0 || pNode->iRowid!=pExpr->pRoot->iRowid || pNode->bEof)
 ){
 pRet[i].bMiss = 1;
 }else{
 pBuf->n = 0;
 }
 }
 }
 return pRet;
}

struct Fts5ExprCtx {
 Fts5Expr *pExpr;
 Fts5PoslistPopulator *aPopulator;
 i64 iOff;
};
typedef struct Fts5ExprCtx Fts5ExprCtx;

/*
** TODO: Make this more efficient!
*/
static int fts5ExprColsetTest(Fts5Colset *pColset, int iCol){
 int i;
 for(i=0; i<pColset->nCol; i++){
 if( pColset->aiCol[i]==iCol ) return 1;
 }
 return 0;
}

/*
** pToken is a buffer nToken bytes in size that may or may not contain
** an embedded 0x00 byte. If it does, return the number of bytes in
** the buffer before the 0x00. If it does not, return nToken.
*/
static int fts5QueryTerm(const char *pToken, int nToken){
 int ii;
 for(ii=0; ii<nToken && pToken[ii]; ii++){}
 return ii;
}

static int fts5ExprPopulatePoslistsCb(
 void *pCtx, /* Copy of 2nd argument to xTokenize() */
 int tflags, /* Mask of FTS5_TOKEN_* flags */
 const char *pToken, /* Pointer to buffer containing token */
 int nToken, /* Size of token in bytes */
 int iUnused1, /* Byte offset of token within input text */
 int iUnused2 /* Byte offset of end of token within input text */
){
 Fts5ExprCtx *p = (Fts5ExprCtx*)pCtx;
 Fts5Expr *pExpr = p->pExpr;
 int i;
 int nQuery = nToken;
 i64 iRowid = pExpr->pRoot->iRowid;

 UNUSED_PARAM2(iUnused1, iUnused2);

 if( nQuery>FTS5_MAX_TOKEN_SIZE ) nQuery = FTS5_MAX_TOKEN_SIZE;
 if( pExpr->pConfig->bTokendata ){
 nQuery = fts5QueryTerm(pToken, nQuery);
 }
 if( (tflags & FTS5_TOKEN_COLOCATED)==0 ) p->iOff++;
 for(i=0; i<pExpr->nPhrase; i++){
 Fts5ExprTerm *pT;
 if( p->aPopulator[i].bOk==0 ) continue;
 for(pT=&pExpr->apExprPhrase[i]->aTerm[0]; pT; pT=pT->pSynonym){
 if( (pT->nQueryTerm==nQuery || (pT->nQueryTerm<nQuery && pT->bPrefix))
 && memcmp(pT->pTerm, pToken, pT->nQueryTerm)==0
 ){
 int rc = sqlite3Fts5PoslistWriterAppend(
 &pExpr->apExprPhrase[i]->poslist, &p->aPopulator[i].writer, p->iOff
 );
 if( rc==SQLITE_OK && pExpr->pConfig->bTokendata && !pT->bPrefix ){
 int iCol = p->iOff>>32;
 int iTokOff = p->iOff & 0x7FFFFFFF;
 rc = sqlite3Fts5IndexIterWriteTokendata(
 pT->pIter, pToken, nToken, iRowid, iCol, iTokOff
 );
 }
 if( rc ) return rc;
 break;
 }
 }
 }
 return SQLITE_OK;
}

static int sqlite3Fts5ExprPopulatePoslists(
 Fts5Config *pConfig,
 Fts5Expr *pExpr,
 Fts5PoslistPopulator *aPopulator,
 int iCol,
 const char *z, int n
){
 int i;
 Fts5ExprCtx sCtx;
 sCtx.pExpr = pExpr;
 sCtx.aPopulator = aPopulator;
 sCtx.iOff = (((i64)iCol) << 32) - 1;

 for(i=0; i<pExpr->nPhrase; i++){
 Fts5ExprNode *pNode = pExpr->apExprPhrase[i]->pNode;
 Fts5Colset *pColset = pNode->pNear->pColset;
 if( (pColset && 0==fts5ExprColsetTest(pColset, iCol))
 || aPopulator[i].bMiss
 ){
 aPopulator[i].bOk = 0;
 }else{
 aPopulator[i].bOk = 1;
 }
 }

 return sqlite3Fts5Tokenize(pConfig,
 FTS5_TOKENIZE_DOCUMENT, z, n, (void*)&sCtx, fts5ExprPopulatePoslistsCb
 );
}

static void fts5ExprClearPoslists(Fts5ExprNode *pNode){
 if( pNode->eType==FTS5_TERM || pNode->eType==FTS5_STRING ){
 pNode->pNear->apPhrase[0]->poslist.n = 0;
 }else{
 int i;
 for(i=0; i<pNode->nChild; i++){
 fts5ExprClearPoslists(pNode->apChild[i]);
 }
 }
}

static int fts5ExprCheckPoslists(Fts5ExprNode *pNode, i64 iRowid){
 pNode->iRowid = iRowid;
 pNode->bEof = 0;
 switch( pNode->eType ){
 case 0:
 case FTS5_TERM:
 case FTS5_STRING:
 return (pNode->pNear->apPhrase[0]->poslist.n>0);

 case FTS5_AND: {
 int i;
 for(i=0; i<pNode->nChild; i++){
 if( fts5ExprCheckPoslists(pNode->apChild[i], iRowid)==0 ){
 fts5ExprClearPoslists(pNode);
 return 0;
 }
 }
 break;
 }

 case FTS5_OR: {
 int i;
 int bRet = 0;
 for(i=0; i<pNode->nChild; i++){
 if( fts5ExprCheckPoslists(pNode->apChild[i], iRowid) ){
 bRet = 1;
 }
 }
 return bRet;
 }

 default: {
 assert( pNode->eType==FTS5_NOT );
 if( 0==fts5ExprCheckPoslists(pNode->apChild[0], iRowid)
 || 0!=fts5ExprCheckPoslists(pNode->apChild[1], iRowid)
 ){
 fts5ExprClearPoslists(pNode);
 return 0;
 }
 break;
 }
 }
 return 1;
}

static void sqlite3Fts5ExprCheckPoslists(Fts5Expr *pExpr, i64 iRowid){
 fts5ExprCheckPoslists(pExpr->pRoot, iRowid);
}

/*
** This function is only called for detail=columns tables.
*/
static int sqlite3Fts5ExprPhraseCollist(
 Fts5Expr *pExpr,
 int iPhrase,
 const u8 **ppCollist,
 int *pnCollist
){
 Fts5ExprPhrase *pPhrase = pExpr->apExprPhrase[iPhrase];
 Fts5ExprNode *pNode = pPhrase->pNode;
 int rc = SQLITE_OK;

 assert( iPhrase>=0 && iPhrase<pExpr->nPhrase );
 assert( pExpr->pConfig->eDetail==FTS5_DETAIL_COLUMNS );

 if( pNode->bEof==0
 && pNode->iRowid==pExpr->pRoot->iRowid
 && pPhrase->poslist.n>0
 ){
 Fts5ExprTerm *pTerm = &pPhrase->aTerm[0];
 if( pTerm->pSynonym ){
 Fts5Buffer *pBuf = (Fts5Buffer*)&pTerm->pSynonym[1];
 rc = fts5ExprSynonymList(
 pTerm, pNode->iRowid, pBuf, (u8**)ppCollist, pnCollist
 );
 }else{
 *ppCollist = pPhrase->aTerm[0].pIter->pData;
 *pnCollist = pPhrase->aTerm[0].pIter->nData;
 }
 }else{
 *ppCollist = 0;
 *pnCollist = 0;
 }

 return rc;
}

/*
** Does the work of the fts5_api.xQueryToken() API method.
*/
static int sqlite3Fts5ExprQueryToken(
 Fts5Expr *pExpr,
 int iPhrase,
 int iToken,
 const char **ppOut,
 int *pnOut
){
 Fts5ExprPhrase *pPhrase = 0;

 if( iPhrase<0 || iPhrase>=pExpr->nPhrase ){
 return SQLITE_RANGE;
 }
 pPhrase = pExpr->apExprPhrase[iPhrase];
 if( iToken<0 || iToken>=pPhrase->nTerm ){
 return SQLITE_RANGE;
 }

 *ppOut = pPhrase->aTerm[iToken].pTerm;
 *pnOut = pPhrase->aTerm[iToken].nFullTerm;
 return SQLITE_OK;
}

/*
** Does the work of the fts5_api.xInstToken() API method.
*/
static int sqlite3Fts5ExprInstToken(
 Fts5Expr *pExpr,
 i64 iRowid,
 int iPhrase,
 int iCol,
 int iOff,
 int iToken,
 const char **ppOut,
 int *pnOut
){
 Fts5ExprPhrase *pPhrase = 0;
 Fts5ExprTerm *pTerm = 0;
 int rc = SQLITE_OK;

 if( iPhrase<0 || iPhrase>=pExpr->nPhrase ){
 return SQLITE_RANGE;
 }
 pPhrase = pExpr->apExprPhrase[iPhrase];
 if( iToken<0 || iToken>=pPhrase->nTerm ){
 return SQLITE_RANGE;
 }
 pTerm = &pPhrase->aTerm[iToken];
 if( pTerm->bPrefix==0 ){
 if( pExpr->pConfig->bTokendata ){
 rc = sqlite3Fts5IterToken(
 pTerm->pIter, iRowid, iCol, iOff+iToken, ppOut, pnOut
 );
 }else{
 *ppOut = pTerm->pTerm;
 *pnOut = pTerm->nFullTerm;
 }
 }
 return rc;
}

/*
** Clear the token mappings for all Fts5IndexIter objects mannaged by
** the expression passed as the only argument.
*/
static void sqlite3Fts5ExprClearTokens(Fts5Expr *pExpr){
 int ii;
 for(ii=0; ii<pExpr->nPhrase; ii++){
 Fts5ExprTerm *pT;
 for(pT=&pExpr->apExprPhrase[ii]->aTerm[0]; pT; pT=pT->pSynonym){
 sqlite3Fts5IndexIterClearTokendata(pT->pIter);
 }
 }
}

#line 1 "fts5_hash.c"
/*
** 2014 August 11
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
*/

/* #include "fts5Int.h" */

typedef struct Fts5HashEntry Fts5HashEntry;

/*
** This file contains the implementation of an in-memory hash table used
** to accumuluate "term -> doclist" content before it is flused to a level-0
** segment.
*/

struct Fts5Hash {
 int eDetail; /* Copy of Fts5Config.eDetail */
 int *pnByte; /* Pointer to bytes counter */
 int nEntry; /* Number of entries currently in hash */
 int nSlot; /* Size of aSlot[] array */
 Fts5HashEntry *pScan; /* Current ordered scan item */
 Fts5HashEntry **aSlot; /* Array of hash slots */
};

/*
** Each entry in the hash table is represented by an object of the
** following type. Each object, its key, and its current data are stored
** in a single memory allocation. The key immediately follows the object
** in memory. The position list data immediately follows the key data
** in memory.
**
** The key is Fts5HashEntry.nKey bytes in size. It consists of a single
** byte identifying the index (either the main term index or a prefix-index),
** followed by the term data. For example: "0token". There is no
** nul-terminator - in this case nKey=6.
**
** The data that follows the key is in a similar, but not identical format
** to the doclist data stored in the database. It is:
**
** * Rowid, as a varint
** * Position list, without 0x00 terminator.
** * Size of previous position list and rowid, as a 4 byte
** big-endian integer.
**
** iRowidOff:
** Offset of last rowid written to data area. Relative to first byte of
** structure.
**
** nData:
** Bytes of data written since iRowidOff.
*/
struct Fts5HashEntry {
 Fts5HashEntry *pHashNext; /* Next hash entry with same hash-key */
 Fts5HashEntry *pScanNext; /* Next entry in sorted order */

 int nAlloc; /* Total size of allocation */
 int iSzPoslist; /* Offset of space for 4-byte poslist size */
 int nData; /* Total bytes of data (incl. structure) */
 int nKey; /* Length of key in bytes */
 u8 bDel; /* Set delete-flag @ iSzPoslist */
 u8 bContent; /* Set content-flag (detail=none mode) */
 i16 iCol; /* Column of last value written */
 int iPos; /* Position of last value written */
 i64 iRowid; /* Rowid of last value written */
};

/*
** Eqivalent to:
**
** char *fts5EntryKey(Fts5HashEntry *pEntry){ return zKey; }
*/
#define fts5EntryKey(p) ( ((char *)(&(p)[1])) )

/*
** Allocate a new hash table.
*/
static int sqlite3Fts5HashNew(Fts5Config *pConfig, Fts5Hash **ppNew, int *pnByte){
 int rc = SQLITE_OK;
 Fts5Hash *pNew;

 *ppNew = pNew = (Fts5Hash*)sqlite3_malloc(sizeof(Fts5Hash));
 if( pNew==0 ){
 rc = SQLITE_NOMEM;
 }else{
 sqlite3_int64 nByte;
 memset(pNew, 0, sizeof(Fts5Hash));
 pNew->pnByte = pnByte;
 pNew->eDetail = pConfig->eDetail;

 pNew->nSlot = 1024;
 nByte = sizeof(Fts5HashEntry*) * pNew->nSlot;
 pNew->aSlot = (Fts5HashEntry**)sqlite3_malloc64(nByte);
 if( pNew->aSlot==0 ){
 sqlite3_free(pNew);
 *ppNew = 0;
 rc = SQLITE_NOMEM;
 }else{
 memset(pNew->aSlot, 0, (size_t)nByte);
 }
 }
 return rc;
}

/*
** Free a hash table object.
*/
static void sqlite3Fts5HashFree(Fts5Hash *pHash){
 if( pHash ){
 sqlite3Fts5HashClear(pHash);
 sqlite3_free(pHash->aSlot);
 sqlite3_free(pHash);
 }
}

/*
** Empty (but do not delete) a hash table.
*/
static void sqlite3Fts5HashClear(Fts5Hash *pHash){
 int i;
 for(i=0; i<pHash->nSlot; i++){
 Fts5HashEntry *pNext;
 Fts5HashEntry *pSlot;
 for(pSlot=pHash->aSlot[i]; pSlot; pSlot=pNext){
 pNext = pSlot->pHashNext;
 sqlite3_free(pSlot);
 }
 }
 memset(pHash->aSlot, 0, pHash->nSlot * sizeof(Fts5HashEntry*));
 pHash->nEntry = 0;
}

static unsigned int fts5HashKey(int nSlot, const u8 *p, int n){
 int i;
 unsigned int h = 13;
 for(i=n-1; i>=0; i--){
 h = (h << 3) ^ h ^ p[i];
 }
 return (h % nSlot);
}

static unsigned int fts5HashKey2(int nSlot, u8 b, const u8 *p, int n){
 int i;
 unsigned int h = 13;
 for(i=n-1; i>=0; i--){
 h = (h << 3) ^ h ^ p[i];
 }
 h = (h << 3) ^ h ^ b;
 return (h % nSlot);
}

/*
** Resize the hash table by doubling the number of slots.
*/
static int fts5HashResize(Fts5Hash *pHash){
 int nNew = pHash->nSlot*2;
 int i;
 Fts5HashEntry **apNew;
 Fts5HashEntry **apOld = pHash->aSlot;

 apNew = (Fts5HashEntry**)sqlite3_malloc64(nNew*sizeof(Fts5HashEntry*));
 if( !apNew ) return SQLITE_NOMEM;
 memset(apNew, 0, nNew*sizeof(Fts5HashEntry*));

 for(i=0; i<pHash->nSlot; i++){
 while( apOld[i] ){
 unsigned int iHash;
 Fts5HashEntry *p = apOld[i];
 apOld[i] = p->pHashNext;
 iHash = fts5HashKey(nNew, (u8*)fts5EntryKey(p), p->nKey);
 p->pHashNext = apNew[iHash];
 apNew[iHash] = p;
 }
 }

 sqlite3_free(apOld);
 pHash->nSlot = nNew;
 pHash->aSlot = apNew;
 return SQLITE_OK;
}

static int fts5HashAddPoslistSize(
 Fts5Hash *pHash,
 Fts5HashEntry *p,
 Fts5HashEntry *p2
){
 int nRet = 0;
 if( p->iSzPoslist ){
 u8 *pPtr = p2 ? (u8*)p2 : (u8*)p;
 int nData = p->nData;
 if( pHash->eDetail==FTS5_DETAIL_NONE ){
 assert( nData==p->iSzPoslist );
 if( p->bDel ){
 pPtr[nData++] = 0x00;
 if( p->bContent ){
 pPtr[nData++] = 0x00;
 }
 }
 }else{
 int nSz = (nData - p->iSzPoslist - 1); /* Size in bytes */
 int nPos = nSz*2 + p->bDel; /* Value of nPos field */

 assert( p->bDel==0 || p->bDel==1 );
 if( nPos<=127 ){
 pPtr[p->iSzPoslist] = (u8)nPos;
 }else{
 int nByte = sqlite3Fts5GetVarintLen((u32)nPos);
 memmove(&pPtr[p->iSzPoslist + nByte], &pPtr[p->iSzPoslist + 1], nSz);
 sqlite3Fts5PutVarint(&pPtr[p->iSzPoslist], nPos);
 nData += (nByte-1);
 }
 }

 nRet = nData - p->nData;
 if( p2==0 ){
 p->iSzPoslist = 0;
 p->bDel = 0;
 p->bContent = 0;
 p->nData = nData;
 }
 }
 return nRet;
}

/*
** Add an entry to the in-memory hash table. The key is the concatenation
** of bByte and (pToken/nToken). The value is (iRowid/iCol/iPos).
**
** (bByte || pToken) -> (iRowid,iCol,iPos)
**
** Or, if iCol is negative, then the value is a delete marker.
*/
static int sqlite3Fts5HashWrite(
 Fts5Hash *pHash,
 i64 iRowid, /* Rowid for this entry */
 int iCol, /* Column token appears in (-ve -> delete) */
 int iPos, /* Position of token within column */
 char bByte, /* First byte of token */
 const char *pToken, int nToken /* Token to add or remove to or from index */
){
 unsigned int iHash;
 Fts5HashEntry *p;
 u8 *pPtr;
 int nIncr = 0; /* Amount to increment (*pHash->pnByte) by */
 int bNew; /* If non-delete entry should be written */

 bNew = (pHash->eDetail==FTS5_DETAIL_FULL);

 /* Attempt to locate an existing hash entry */
 iHash = fts5HashKey2(pHash->nSlot, (u8)bByte, (const u8*)pToken, nToken);
 for(p=pHash->aSlot[iHash]; p; p=p->pHashNext){
 char *zKey = fts5EntryKey(p);
 if( zKey[0]==bByte
 && p->nKey==nToken+1
 && memcmp(&zKey[1], pToken, nToken)==0
 ){
 break;
 }
 }

 /* If an existing hash entry cannot be found, create a new one. */
 if( p==0 ){
 /* Figure out how much space to allocate */
 char *zKey;
 sqlite3_int64 nByte = sizeof(Fts5HashEntry) + (nToken+1) + 1 + 64;
 if( nByte<128 ) nByte = 128;

 /* Grow the Fts5Hash.aSlot[] array if necessary. */
 if( (pHash->nEntry*2)>=pHash->nSlot ){
 int rc = fts5HashResize(pHash);
 if( rc!=SQLITE_OK ) return rc;
 iHash = fts5HashKey2(pHash->nSlot, (u8)bByte, (const u8*)pToken, nToken);
 }

 /* Allocate new Fts5HashEntry and add it to the hash table. */
 p = (Fts5HashEntry*)sqlite3_malloc64(nByte);
 if( !p ) return SQLITE_NOMEM;
 memset(p, 0, sizeof(Fts5HashEntry));
 p->nAlloc = (int)nByte;
 zKey = fts5EntryKey(p);
 zKey[0] = bByte;
 memcpy(&zKey[1], pToken, nToken);
 assert( iHash==fts5HashKey(pHash->nSlot, (u8*)zKey, nToken+1) );
 p->nKey = nToken+1;
 zKey[nToken+1] = '\0';
 p->nData = nToken+1 + sizeof(Fts5HashEntry);
 p->pHashNext = pHash->aSlot[iHash];
 pHash->aSlot[iHash] = p;
 pHash->nEntry++;

 /* Add the first rowid field to the hash-entry */
 p->nData += sqlite3Fts5PutVarint(&((u8*)p)[p->nData], iRowid);
 p->iRowid = iRowid;

 p->iSzPoslist = p->nData;
 if( pHash->eDetail!=FTS5_DETAIL_NONE ){
 p->nData += 1;
 p->iCol = (pHash->eDetail==FTS5_DETAIL_FULL ? 0 : -1);
 }

 }else{

 /* Appending to an existing hash-entry. Check that there is enough
 ** space to append the largest possible new entry. Worst case scenario
 ** is:
 **
 ** + 9 bytes for a new rowid,
 ** + 4 byte reserved for the "poslist size" varint.
 ** + 1 byte for a "new column" byte,
 ** + 3 bytes for a new column number (16-bit max) as a varint,
 ** + 5 bytes for the new position offset (32-bit max).
 */
 if( (p->nAlloc - p->nData) < (9 + 4 + 1 + 3 + 5) ){
 sqlite3_int64 nNew = p->nAlloc * 2;
 Fts5HashEntry *pNew;
 Fts5HashEntry **pp;
 pNew = (Fts5HashEntry*)sqlite3_realloc64(p, nNew);
 if( pNew==0 ) return SQLITE_NOMEM;
 pNew->nAlloc = (int)nNew;
 for(pp=&pHash->aSlot[iHash]; *pp!=p; pp=&(*pp)->pHashNext);
 *pp = pNew;
 p = pNew;
 }
 nIncr -= p->nData;
 }
 assert( (p->nAlloc - p->nData) >= (9 + 4 + 1 + 3 + 5) );

 pPtr = (u8*)p;

 /* If this is a new rowid, append the 4-byte size field for the previous
 ** entry, and the new rowid for this entry. */
 if( iRowid!=p->iRowid ){
 u64 iDiff = (u64)iRowid - (u64)p->iRowid;
 fts5HashAddPoslistSize(pHash, p, 0);
 p->nData += sqlite3Fts5PutVarint(&pPtr[p->nData], iDiff);
 p->iRowid = iRowid;
 bNew = 1;
 p->iSzPoslist = p->nData;
 if( pHash->eDetail!=FTS5_DETAIL_NONE ){
 p->nData += 1;
 p->iCol = (pHash->eDetail==FTS5_DETAIL_FULL ? 0 : -1);
 p->iPos = 0;
 }
 }

 if( iCol>=0 ){
 if( pHash->eDetail==FTS5_DETAIL_NONE ){
 p->bContent = 1;
 }else{
 /* Append a new column value, if necessary */
 assert_nc( iCol>=p->iCol );
 if( iCol!=p->iCol ){
 if( pHash->eDetail==FTS5_DETAIL_FULL ){
 pPtr[p->nData++] = 0x01;
 p->nData += sqlite3Fts5PutVarint(&pPtr[p->nData], iCol);
 p->iCol = (i16)iCol;
 p->iPos = 0;
 }else{
 bNew = 1;
 p->iCol = (i16)(iPos = iCol);
 }
 }

 /* Append the new position offset, if necessary */
 if( bNew ){
 p->nData += sqlite3Fts5PutVarint(&pPtr[p->nData], iPos - p->iPos + 2);
 p->iPos = iPos;
 }
 }
 }else{
 /* This is a delete. Set the delete flag. */
 p->bDel = 1;
 }

 nIncr += p->nData;
 *pHash->pnByte += nIncr;
 return SQLITE_OK;
}

/*
** Arguments pLeft and pRight point to linked-lists of hash-entry objects,
** each sorted in key order. This function merges the two lists into a
** single list and returns a pointer to its first element.
*/
static Fts5HashEntry *fts5HashEntryMerge(
 Fts5HashEntry *pLeft,
 Fts5HashEntry *pRight
){
 Fts5HashEntry *p1 = pLeft;
 Fts5HashEntry *p2 = pRight;
 Fts5HashEntry *pRet = 0;
 Fts5HashEntry **ppOut = &pRet;

 while( p1 || p2 ){
 if( p1==0 ){
 *ppOut = p2;
 p2 = 0;
 }else if( p2==0 ){
 *ppOut = p1;
 p1 = 0;
 }else{
 char *zKey1 = fts5EntryKey(p1);
 char *zKey2 = fts5EntryKey(p2);
 int nMin = MIN(p1->nKey, p2->nKey);

 int cmp = memcmp(zKey1, zKey2, nMin);
 if( cmp==0 ){
 cmp = p1->nKey - p2->nKey;
 }
 assert( cmp!=0 );

 if( cmp>0 ){
 /* p2 is smaller */
 *ppOut = p2;
 ppOut = &p2->pScanNext;
 p2 = p2->pScanNext;
 }else{
 /* p1 is smaller */
 *ppOut = p1;
 ppOut = &p1->pScanNext;
 p1 = p1->pScanNext;
 }
 *ppOut = 0;
 }
 }

 return pRet;
}

/*
** Link all tokens from hash table iHash into a list in sorted order. The
** tokens are not removed from the hash table.
*/
static int fts5HashEntrySort(
 Fts5Hash *pHash,
 const char *pTerm, int nTerm, /* Query prefix, if any */
 Fts5HashEntry **ppSorted
){
 const int nMergeSlot = 32;
 Fts5HashEntry **ap;
 Fts5HashEntry *pList;
 int iSlot;
 int i;

 *ppSorted = 0;
 ap = sqlite3_malloc64(sizeof(Fts5HashEntry*) * nMergeSlot);
 if( !ap ) return SQLITE_NOMEM;
 memset(ap, 0, sizeof(Fts5HashEntry*) * nMergeSlot);

 for(iSlot=0; iSlot<pHash->nSlot; iSlot++){
 Fts5HashEntry *pIter;
 for(pIter=pHash->aSlot[iSlot]; pIter; pIter=pIter->pHashNext){
 if( pTerm==0
 || (pIter->nKey>=nTerm && 0==memcmp(fts5EntryKey(pIter), pTerm, nTerm))
 ){
 Fts5HashEntry *pEntry = pIter;
 pEntry->pScanNext = 0;
 for(i=0; ap[i]; i++){
 pEntry = fts5HashEntryMerge(pEntry, ap[i]);
 ap[i] = 0;
 }
 ap[i] = pEntry;
 }
 }
 }

 pList = 0;
 for(i=0; i<nMergeSlot; i++){
 pList = fts5HashEntryMerge(pList, ap[i]);
 }

 sqlite3_free(ap);
 *ppSorted = pList;
 return SQLITE_OK;
}

/*
** Query the hash table for a doclist associated with term pTerm/nTerm.
*/
static int sqlite3Fts5HashQuery(
 Fts5Hash *pHash, /* Hash table to query */
 int nPre,
 const char *pTerm, int nTerm, /* Query term */
 void **ppOut, /* OUT: Pointer to new object */
 int *pnDoclist /* OUT: Size of doclist in bytes */
){
 unsigned int iHash = fts5HashKey(pHash->nSlot, (const u8*)pTerm, nTerm);
 char *zKey = 0;
 Fts5HashEntry *p;

 for(p=pHash->aSlot[iHash]; p; p=p->pHashNext){
 zKey = fts5EntryKey(p);
 if( nTerm==p->nKey && memcmp(zKey, pTerm, nTerm)==0 ) break;
 }

 if( p ){
 int nHashPre = sizeof(Fts5HashEntry) + nTerm;
 int nList = p->nData - nHashPre;
 u8 *pRet = (u8*)(*ppOut = sqlite3_malloc64(nPre + nList + 10));
 if( pRet ){
 Fts5HashEntry *pFaux = (Fts5HashEntry*)&pRet[nPre-nHashPre];
 memcpy(&pRet[nPre], &((u8*)p)[nHashPre], nList);
 nList += fts5HashAddPoslistSize(pHash, p, pFaux);
 *pnDoclist = nList;
 }else{
 *pnDoclist = 0;
 return SQLITE_NOMEM;
 }
 }else{
 *ppOut = 0;
 *pnDoclist = 0;
 }

 return SQLITE_OK;
}

static int sqlite3Fts5HashScanInit(
 Fts5Hash *p, /* Hash table to query */
 const char *pTerm, int nTerm /* Query prefix */
){
 return fts5HashEntrySort(p, pTerm, nTerm, &p->pScan);
}

#ifdef SQLITE_DEBUG
static int fts5HashCount(Fts5Hash *pHash){
 int nEntry = 0;
 int ii;
 for(ii=0; ii<pHash->nSlot; ii++){
 Fts5HashEntry *p = 0;
 for(p=pHash->aSlot[ii]; p; p=p->pHashNext){
 nEntry++;
 }
 }
 return nEntry;
}
#endif

/*
** Return true if the hash table is empty, false otherwise.
*/
static int sqlite3Fts5HashIsEmpty(Fts5Hash *pHash){
 assert( pHash->nEntry==fts5HashCount(pHash) );
 return pHash->nEntry==0;
}

static void sqlite3Fts5HashScanNext(Fts5Hash *p){
 assert( !sqlite3Fts5HashScanEof(p) );
 p->pScan = p->pScan->pScanNext;
}

static int sqlite3Fts5HashScanEof(Fts5Hash *p){
 return (p->pScan==0);
}

static void sqlite3Fts5HashScanEntry(
 Fts5Hash *pHash,
 const char **pzTerm, /* OUT: term (nul-terminated) */
 int *pnTerm, /* OUT: Size of term in bytes */
 const u8 **ppDoclist, /* OUT: pointer to doclist */
 int *pnDoclist /* OUT: size of doclist in bytes */
){
 Fts5HashEntry *p;
 if( (p = pHash->pScan) ){
 char *zKey = fts5EntryKey(p);
 int nTerm = p->nKey;
 fts5HashAddPoslistSize(pHash, p, 0);
 *pzTerm = zKey;
 *pnTerm = nTerm;
 *ppDoclist = (const u8*)&zKey[nTerm];
 *pnDoclist = p->nData - (sizeof(Fts5HashEntry) + nTerm);
 }else{
 *pzTerm = 0;
 *pnTerm = 0;
 *ppDoclist = 0;
 *pnDoclist = 0;
 }
}

#line 1 "fts5_index.c"
/*
** 2014 May 31
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** Low level access to the FTS index stored in the database file. The
** routines in this file file implement all read and write access to the
** %_data table. Other parts of the system access this functionality via
** the interface defined in fts5Int.h.
*/

/* #include "fts5Int.h" */

/*
** Overview:
**
** The %_data table contains all the FTS indexes for an FTS5 virtual table.
** As well as the main term index, there may be up to 31 prefix indexes.
** The format is similar to FTS3/4, except that:
**
** * all segment b-tree leaf data is stored in fixed size page records
** (e.g. 1000 bytes). A single doclist may span multiple pages. Care is
** taken to ensure it is possible to iterate in either direction through
** the entries in a doclist, or to seek to a specific entry within a
** doclist, without loading it into memory.
**
** * large doclists that span many pages have associated "doclist index"
** records that contain a copy of the first rowid on each page spanned by
** the doclist. This is used to speed up seek operations, and merges of
** large doclists with very small doclists.
**
** * extra fields in the "structure record" record the state of ongoing
** incremental merge operations.
**
*/

#define FTS5_OPT_WORK_UNIT 1000 /* Number of leaf pages per optimize step */
#define FTS5_WORK_UNIT 64 /* Number of leaf pages in unit of work */

#define FTS5_MIN_DLIDX_SIZE 4 /* Add dlidx if this many empty pages */

#define FTS5_MAIN_PREFIX '0'

#if FTS5_MAX_PREFIX_INDEXES > 31
# error "FTS5_MAX_PREFIX_INDEXES is too large"
#endif

#define FTS5_MAX_LEVEL 64

/*
** There are two versions of the format used for the structure record:
**
** 1. the legacy format, that may be read by all fts5 versions, and
**
** 2. the V2 format, which is used by contentless_delete=1 databases.
**
** Both begin with a 4-byte "configuration cookie" value. Then, a legacy
** format structure record contains a varint - the number of levels in
** the structure. Whereas a V2 structure record contains the constant
** 4 bytes [0xff 0x00 0x00 0x01]. This is unambiguous as the value of a
** varint has to be at least 16256 to begin with "0xFF". And the default
** maximum number of levels is 64.
**
** See below for more on structure record formats.
*/
#define FTS5_STRUCTURE_V2 "\xFF\x00\x00\x01"

/*
** Details:
**
** The %_data table managed by this module,
**
** CREATE TABLE %_data(id INTEGER PRIMARY KEY, block BLOB);
**
** , contains the following 6 types of records. See the comments surrounding
** the FTS5_*_ROWID macros below for a description of how %_data rowids are
** assigned to each fo them.
**
** 1. Structure Records:
**
** The set of segments that make up an index - the index structure - are
** recorded in a single record within the %_data table. The record consists
** of a single 32-bit configuration cookie value followed by a list of
** SQLite varints.
**
** If the structure record is a V2 record, the configuration cookie is
** followed by the following 4 bytes: [0xFF 0x00 0x00 0x01].
**
** Next, the record continues with three varints:
**
** + number of levels,
** + total number of segments on all levels,
** + value of write counter.
**
** Then, for each level from 0 to nMax:
**
** + number of input segments in ongoing merge.
** + total number of segments in level.
** + for each segment from oldest to newest:
** + segment id (always > 0)
** + first leaf page number (often 1, always greater than 0)
** + final leaf page number
**
** Then, for V2 structures only:
**
** + lower origin counter value,
** + upper origin counter value,
** + the number of tombstone hash pages.
**
** 2. The Averages Record:
**
** A single record within the %_data table. The data is a list of varints.
** The first value is the number of rows in the index. Then, for each column
** from left to right, the total number of tokens in the column for all
** rows of the table.
**
** 3. Segment leaves:
**
** TERM/DOCLIST FORMAT:
**
** Most of each segment leaf is taken up by term/doclist data. The
** general format of term/doclist, starting with the first term
** on the leaf page, is:
**
** varint : size of first term
** blob: first term data
** doclist: first doclist
** zero-or-more {
** varint: number of bytes in common with previous term
** varint: number of bytes of new term data (nNew)
** blob: nNew bytes of new term data
** doclist: next doclist
** }
**
** doclist format:
**
** varint: first rowid
** poslist: first poslist
** zero-or-more {
** varint: rowid delta (always > 0)
** poslist: next poslist
** }
**
** poslist format:
**
** varint: size of poslist in bytes multiplied by 2, not including
** this field. Plus 1 if this entry carries the "delete" flag.
** collist: collist for column 0
** zero-or-more {
** 0x01 byte
** varint: column number (I)
** collist: collist for column I
** }
**
** collist format:
**
** varint: first offset + 2
** zero-or-more {
** varint: offset delta + 2
** }
**
** PAGE FORMAT
**
** Each leaf page begins with a 4-byte header containing 2 16-bit
** unsigned integer fields in big-endian format. They are:
**
** * The byte offset of the first rowid on the page, if it exists
** and occurs before the first term (otherwise 0).
**
** * The byte offset of the start of the page footer. If the page
** footer is 0 bytes in size, then this field is the same as the
** size of the leaf page in bytes.
**
** The page footer consists of a single varint for each term located
** on the page. Each varint is the byte offset of the current term
** within the page, delta-compressed against the previous value. In
** other words, the first varint in the footer is the byte offset of
** the first term, the second is the byte offset of the second less that
** of the first, and so on.
**
** The term/doclist format described above is accurate if the entire
** term/doclist data fits on a single leaf page. If this is not the case,
** the format is changed in two ways:
**
** + if the first rowid on a page occurs before the first term, it
** is stored as a literal value:
**
** varint: first rowid
**
** + the first term on each page is stored in the same way as the
** very first term of the segment:
**
** varint : size of first term
** blob: first term data
**
** 5. Segment doclist indexes:
**
** Doclist indexes are themselves b-trees, however they usually consist of
** a single leaf record only. The format of each doclist index leaf page
** is:
**
** * Flags byte. Bits are:
** 0x01: Clear if leaf is also the root page, otherwise set.
**
** * Page number of fts index leaf page. As a varint.
**
** * First rowid on page indicated by previous field. As a varint.
**
** * A list of varints, one for each subsequent termless page. A
** positive delta if the termless page contains at least one rowid,
** or an 0x00 byte otherwise.
**
** Internal doclist index nodes are:
**
** * Flags byte. Bits are:
** 0x01: Clear for root page, otherwise set.
**
** * Page number of first child page. As a varint.
**
** * Copy of first rowid on page indicated by previous field. As a varint.
**
** * A list of delta-encoded varints - the first rowid on each subsequent
** child page.
**
** 6. Tombstone Hash Page
**
** These records are only ever present in contentless_delete=1 tables.
** There are zero or more of these associated with each segment. They
** are used to store the tombstone rowids for rows contained in the
** associated segments.
**
** The set of nHashPg tombstone hash pages associated with a single
** segment together form a single hash table containing tombstone rowids.
** To find the page of the hash on which a key might be stored:
**
** iPg = (rowid % nHashPg)
**
** Then, within page iPg, which has nSlot slots:
**
** iSlot = (rowid / nHashPg) % nSlot
**
** Each tombstone hash page begins with an 8 byte header:
**
** 1-byte: Key-size (the size in bytes of each slot). Either 4 or 8.
** 1-byte: rowid-0-tombstone flag. This flag is only valid on the
** first tombstone hash page for each segment (iPg=0). If set,
** the hash table contains rowid 0. If clear, it does not.
** Rowid 0 is handled specially.
** 2-bytes: unused.
** 4-bytes: Big-endian integer containing number of entries on page.
**
** Following this are nSlot 4 or 8 byte slots (depending on the key-size
** in the first byte of the page header). The number of slots may be
** determined based on the size of the page record and the key-size:
**
** nSlot = (nByte - 8) / key-size
*/

/*
** Rowids for the averages and structure records in the %_data table.
*/
#define FTS5_AVERAGES_ROWID 1 /* Rowid used for the averages record */
#define FTS5_STRUCTURE_ROWID 10 /* The structure record */

/*
** Macros determining the rowids used by segment leaves and dlidx leaves
** and nodes. All nodes and leaves are stored in the %_data table with large
** positive rowids.
**
** Each segment has a unique non-zero 16-bit id.
**
** The rowid for each segment leaf is found by passing the segment id and
** the leaf page number to the FTS5_SEGMENT_ROWID macro. Leaves are numbered
** sequentially starting from 1.
*/
#define FTS5_DATA_ID_B 16 /* Max seg id number 65535 */
#define FTS5_DATA_DLI_B 1 /* Doclist-index flag (1 bit) */
#define FTS5_DATA_HEIGHT_B 5 /* Max dlidx tree height of 32 */
#define FTS5_DATA_PAGE_B 31 /* Max page number of 2147483648 */

#define fts5_dri(segid, dlidx, height, pgno) ( \
((i64)(segid) << (FTS5_DATA_PAGE_B+FTS5_DATA_HEIGHT_B+FTS5_DATA_DLI_B)) + \
((i64)(dlidx) << (FTS5_DATA_PAGE_B + FTS5_DATA_HEIGHT_B)) + \
((i64)(height) << (FTS5_DATA_PAGE_B)) + \
((i64)(pgno)) \
)

#define FTS5_SEGMENT_ROWID(segid, pgno) fts5_dri(segid, 0, 0, pgno)
#define FTS5_DLIDX_ROWID(segid, height, pgno) fts5_dri(segid, 1, height, pgno)
#define FTS5_TOMBSTONE_ROWID(segid,ipg) fts5_dri(segid+(1<<16), 0, 0, ipg)

#ifdef SQLITE_DEBUG
static int sqlite3Fts5Corrupt() { return SQLITE_CORRUPT_VTAB; }
#endif

/*
** Each time a blob is read from the %_data table, it is padded with this
** many zero bytes. This makes it easier to decode the various record formats
** without overreading if the records are corrupt.
*/
#define FTS5_DATA_ZERO_PADDING 8
#define FTS5_DATA_PADDING 20

typedef struct Fts5Data Fts5Data;
typedef struct Fts5DlidxIter Fts5DlidxIter;
typedef struct Fts5DlidxLvl Fts5DlidxLvl;
typedef struct Fts5DlidxWriter Fts5DlidxWriter;
typedef struct Fts5Iter Fts5Iter;
typedef struct Fts5PageWriter Fts5PageWriter;
typedef struct Fts5SegIter Fts5SegIter;
typedef struct Fts5DoclistIter Fts5DoclistIter;
typedef struct Fts5SegWriter Fts5SegWriter;
typedef struct Fts5Structure Fts5Structure;
typedef struct Fts5StructureLevel Fts5StructureLevel;
typedef struct Fts5StructureSegment Fts5StructureSegment;
typedef struct Fts5TokenDataIter Fts5TokenDataIter;
typedef struct Fts5TokenDataMap Fts5TokenDataMap;
typedef struct Fts5TombstoneArray Fts5TombstoneArray;

struct Fts5Data {
 u8 *p; /* Pointer to buffer containing record */
 int nn; /* Size of record in bytes */
 int szLeaf; /* Size of leaf without page-index */
};

/*
** One object per %_data table.
**
** nContentlessDelete:
** The number of contentless delete operations since the most recent
** call to fts5IndexFlush() or fts5IndexDiscardData(). This is tracked
** so that extra auto-merge work can be done by fts5IndexFlush() to
** account for the delete operations.
*/
struct Fts5Index {
 Fts5Config *pConfig; /* Virtual table configuration */
 char *zDataTbl; /* Name of %_data table */
 int nWorkUnit; /* Leaf pages in a "unit" of work */

 /*
 ** Variables related to the accumulation of tokens and doclists within the
 ** in-memory hash tables before they are flushed to disk.
 */
 Fts5Hash *pHash; /* Hash table for in-memory data */
 int nPendingData; /* Current bytes of pending data */
 i64 iWriteRowid; /* Rowid for current doc being written */
 int bDelete; /* Current write is a delete */
 int nContentlessDelete; /* Number of contentless delete ops */
 int nPendingRow; /* Number of INSERT in hash table */

 /* Error state. */
 int rc; /* Current error code */
 int flushRc;

 /* State used by the fts5DataXXX() functions. */
 sqlite3_blob *pReader; /* RO incr-blob open on %_data table */
 sqlite3_stmt *pWriter; /* "INSERT ... %_data VALUES(?,?)" */
 sqlite3_stmt *pDeleter; /* "DELETE FROM %_data ... id>=? AND id<=?" */
 sqlite3_stmt *pIdxWriter; /* "INSERT ... %_idx VALUES(?,?,?,?)" */
 sqlite3_stmt *pIdxDeleter; /* "DELETE FROM %_idx WHERE segid=?" */
 sqlite3_stmt *pIdxSelect;
 sqlite3_stmt *pIdxNextSelect;
 int nRead; /* Total number of blocks read */

 sqlite3_stmt *pDeleteFromIdx;

 sqlite3_stmt *pDataVersion;
 i64 iStructVersion; /* data_version when pStruct read */
 Fts5Structure *pStruct; /* Current db structure (or NULL) */
};

struct Fts5DoclistIter {
 u8 *aEof; /* Pointer to 1 byte past end of doclist */

 /* Output variables. aPoslist==0 at EOF */
 i64 iRowid;
 u8 *aPoslist;
 int nPoslist;
 int nSize;
};

/*
** The contents of the "structure" record for each index are represented
** using an Fts5Structure record in memory. Which uses instances of the
** other Fts5StructureXXX types as components.
**
** nOriginCntr:
** This value is set to non-zero for structure records created for
** contentlessdelete=1 tables only. In that case it represents the
** origin value to apply to the next top-level segment created.
*/
struct Fts5StructureSegment {
 int iSegid; /* Segment id */
 int pgnoFirst; /* First leaf page number in segment */
 int pgnoLast; /* Last leaf page number in segment */

 /* contentlessdelete=1 tables only: */
 u64 iOrigin1;
 u64 iOrigin2;
 int nPgTombstone; /* Number of tombstone hash table pages */
 u64 nEntryTombstone; /* Number of tombstone entries that "count" */
 u64 nEntry; /* Number of rows in this segment */
};
struct Fts5StructureLevel {
 int nMerge; /* Number of segments in incr-merge */
 int nSeg; /* Total number of segments on level */
 Fts5StructureSegment *aSeg; /* Array of segments. aSeg[0] is oldest. */
};
struct Fts5Structure {
 int nRef; /* Object reference count */
 u64 nWriteCounter; /* Total leaves written to level 0 */
 u64 nOriginCntr; /* Origin value for next top-level segment */
 int nSegment; /* Total segments in this structure */
 int nLevel; /* Number of levels in this index */
 Fts5StructureLevel aLevel[1]; /* Array of nLevel level objects */
};

/*
** An object of type Fts5SegWriter is used to write to segments.
*/
struct Fts5PageWriter {
 int pgno; /* Page number for this page */
 int iPrevPgidx; /* Previous value written into pgidx */
 Fts5Buffer buf; /* Buffer containing leaf data */
 Fts5Buffer pgidx; /* Buffer containing page-index */
 Fts5Buffer term; /* Buffer containing previous term on page */
};
struct Fts5DlidxWriter {
 int pgno; /* Page number for this page */
 int bPrevValid; /* True if iPrev is valid */
 i64 iPrev; /* Previous rowid value written to page */
 Fts5Buffer buf; /* Buffer containing page data */
};
struct Fts5SegWriter {
 int iSegid; /* Segid to write to */
 Fts5PageWriter writer; /* PageWriter object */
 i64 iPrevRowid; /* Previous rowid written to current leaf */
 u8 bFirstRowidInDoclist; /* True if next rowid is first in doclist */
 u8 bFirstRowidInPage; /* True if next rowid is first in page */
 /* TODO1: Can use (writer.pgidx.n==0) instead of bFirstTermInPage */
 u8 bFirstTermInPage; /* True if next term will be first in leaf */
 int nLeafWritten; /* Number of leaf pages written */
 int nEmpty; /* Number of contiguous term-less nodes */

 int nDlidx; /* Allocated size of aDlidx[] array */
 Fts5DlidxWriter *aDlidx; /* Array of Fts5DlidxWriter objects */

 /* Values to insert into the %_idx table */
 Fts5Buffer btterm; /* Next term to insert into %_idx table */
 int iBtPage; /* Page number corresponding to btterm */
};

typedef struct Fts5CResult Fts5CResult;
struct Fts5CResult {
 u16 iFirst; /* aSeg[] index of firstest iterator */
 u8 bTermEq; /* True if the terms are equal */
};

/*
** Object for iterating through a single segment, visiting each term/rowid
** pair in the segment.
**
** pSeg:
** The segment to iterate through.
**
** iLeafPgno:
** Current leaf page number within segment.
**
** iLeafOffset:
** Byte offset within the current leaf that is the first byte of the
** position list data (one byte passed the position-list size field).
**
** pLeaf:
** Buffer containing current leaf page data. Set to NULL at EOF.
**
** iTermLeafPgno, iTermLeafOffset:
** Leaf page number containing the last term read from the segment. And
** the offset immediately following the term data.
**
** flags:
** Mask of FTS5_SEGITER_XXX values. Interpreted as follows:
**
** FTS5_SEGITER_ONETERM:
** If set, set the iterator to point to EOF after the current doclist
** has been exhausted. Do not proceed to the next term in the segment.
**
** FTS5_SEGITER_REVERSE:
** This flag is only ever set if FTS5_SEGITER_ONETERM is also set. If
** it is set, iterate through rowid in descending order instead of the
** default ascending order.
**
** iRowidOffset/nRowidOffset/aRowidOffset:
** These are used if the FTS5_SEGITER_REVERSE flag is set.
**
** For each rowid on the page corresponding to the current term, the
** corresponding aRowidOffset[] entry is set to the byte offset of the
** start of the "position-list-size" field within the page.
**
** iTermIdx:
** Index of current term on iTermLeafPgno.
**
** apTombstone/nTombstone:
** These are used for contentless_delete=1 tables only. When the cursor
** is first allocated, the apTombstone[] array is allocated so that it
** is large enough for all tombstones hash pages associated with the
** segment. The pages themselves are loaded lazily from the database as
** they are required.
*/
struct Fts5SegIter {
 Fts5StructureSegment *pSeg; /* Segment to iterate through */
 int flags; /* Mask of configuration flags */
 int iLeafPgno; /* Current leaf page number */
 Fts5Data *pLeaf; /* Current leaf data */
 Fts5Data *pNextLeaf; /* Leaf page (iLeafPgno+1) */
 i64 iLeafOffset; /* Byte offset within current leaf */
 Fts5TombstoneArray *pTombArray; /* Array of tombstone pages */

 /* Next method */
 void (*xNext)(Fts5Index*, Fts5SegIter*, int*);

 /* The page and offset from which the current term was read. The offset
 ** is the offset of the first rowid in the current doclist. */
 int iTermLeafPgno;
 int iTermLeafOffset;

 int iPgidxOff; /* Next offset in pgidx */
 int iEndofDoclist;

 /* The following are only used if the FTS5_SEGITER_REVERSE flag is set. */
 int iRowidOffset; /* Current entry in aRowidOffset[] */
 int nRowidOffset; /* Allocated size of aRowidOffset[] array */
 int *aRowidOffset; /* Array of offset to rowid fields */

 Fts5DlidxIter *pDlidx; /* If there is a doclist-index */

 /* Variables populated based on current entry. */
 Fts5Buffer term; /* Current term */
 i64 iRowid; /* Current rowid */
 int nPos; /* Number of bytes in current position list */
 u8 bDel; /* True if the delete flag is set */
};

/*
** Array of tombstone pages. Reference counted.
*/
struct Fts5TombstoneArray {
 int nRef; /* Number of pointers to this object */
 int nTombstone;
 Fts5Data *apTombstone[1]; /* Array of tombstone pages */
};

/*
** Argument is a pointer to an Fts5Data structure that contains a
** leaf page.
*/
#define ASSERT_SZLEAF_OK(x) assert( \
 (x)->szLeaf==(x)->nn || (x)->szLeaf==fts5GetU16(&(x)->p[2]) \
)

#define FTS5_SEGITER_ONETERM 0x01
#define FTS5_SEGITER_REVERSE 0x02

/*
** Argument is a pointer to an Fts5Data structure that contains a leaf
** page. This macro evaluates to true if the leaf contains no terms, or
** false if it contains at least one term.
*/
#define fts5LeafIsTermless(x) ((x)->szLeaf >= (x)->nn)

#define fts5LeafTermOff(x, i) (fts5GetU16(&(x)->p[(x)->szLeaf + (i)*2]))

#define fts5LeafFirstRowidOff(x) (fts5GetU16((x)->p))

/*
** Object for iterating through the merged results of one or more segments,
** visiting each term/rowid pair in the merged data.
**
** nSeg is always a power of two greater than or equal to the number of
** segments that this object is merging data from. Both the aSeg[] and
** aFirst[] arrays are sized at nSeg entries. The aSeg[] array is padded
** with zeroed objects - these are handled as if they were iterators opened
** on empty segments.
**
** The results of comparing segments aSeg[N] and aSeg[N+1], where N is an
** even number, is stored in aFirst[(nSeg+N)/2]. The "result" of the
** comparison in this context is the index of the iterator that currently
** points to the smaller term/rowid combination. Iterators at EOF are
** considered to be greater than all other iterators.
**
** aFirst[1] contains the index in aSeg[] of the iterator that points to
** the smallest key overall. aFirst[0] is unused.
**
** poslist:
** Used by sqlite3Fts5IterPoslist() when the poslist needs to be buffered.
** There is no way to tell if this is populated or not.
**
** pColset:
** If not NULL, points to an object containing a set of column indices.
** Only matches that occur in one of these columns will be returned.
** The Fts5Iter does not own the Fts5Colset object, and so it is not
** freed when the iterator is closed - it is owned by the upper layer.
*/
struct Fts5Iter {
 Fts5IndexIter base; /* Base class containing output vars */
 Fts5TokenDataIter *pTokenDataIter;

 Fts5Index *pIndex; /* Index that owns this iterator */
 Fts5Buffer poslist; /* Buffer containing current poslist */
 Fts5Colset *pColset; /* Restrict matches to these columns */

 /* Invoked to set output variables. */
 void (*xSetOutputs)(Fts5Iter*, Fts5SegIter*);

 int nSeg; /* Size of aSeg[] array */
 int bRev; /* True to iterate in reverse order */
 u8 bSkipEmpty; /* True to skip deleted entries */

 i64 iSwitchRowid; /* Firstest rowid of other than aFirst[1] */
 Fts5CResult *aFirst; /* Current merge state (see above) */
 Fts5SegIter aSeg[1]; /* Array of segment iterators */
};

/*
** An instance of the following type is used to iterate through the contents
** of a doclist-index record.
**
** pData:
** Record containing the doclist-index data.
**
** bEof:
** Set to true once iterator has reached EOF.
**
** iOff:
** Set to the current offset within record pData.
*/
struct Fts5DlidxLvl {
 Fts5Data *pData; /* Data for current page of this level */
 int iOff; /* Current offset into pData */
 int bEof; /* At EOF already */
 int iFirstOff; /* Used by reverse iterators */

 /* Output variables */
 int iLeafPgno; /* Page number of current leaf page */
 i64 iRowid; /* First rowid on leaf iLeafPgno */
};
struct Fts5DlidxIter {
 int nLvl;
 int iSegid;
 Fts5DlidxLvl aLvl[1];
};

static void fts5PutU16(u8 *aOut, u16 iVal){
 aOut[0] = (iVal>>8);
 aOut[1] = (iVal&0xFF);
}

static u16 fts5GetU16(const u8 *aIn){
 return ((u16)aIn[0] << 8) + aIn[1];
}

/*
** The only argument points to a buffer at least 8 bytes in size. This
** function interprets the first 8 bytes of the buffer as a 64-bit big-endian
** unsigned integer and returns the result.
*/
static u64 fts5GetU64(u8 *a){
 return ((u64)a[0] << 56)
 + ((u64)a[1] << 48)
 + ((u64)a[2] << 40)
 + ((u64)a[3] << 32)
 + ((u64)a[4] << 24)
 + ((u64)a[5] << 16)
 + ((u64)a[6] << 8)
 + ((u64)a[7] << 0);
}

/*
** The only argument points to a buffer at least 4 bytes in size. This
** function interprets the first 4 bytes of the buffer as a 32-bit big-endian
** unsigned integer and returns the result.
*/
static u32 fts5GetU32(const u8 *a){
 return ((u32)a[0] << 24)
 + ((u32)a[1] << 16)
 + ((u32)a[2] << 8)
 + ((u32)a[3] << 0);
}

/*
** Write iVal, formated as a 64-bit big-endian unsigned integer, to the
** buffer indicated by the first argument.
*/
static void fts5PutU64(u8 *a, u64 iVal){
 a[0] = ((iVal >> 56) & 0xFF);
 a[1] = ((iVal >> 48) & 0xFF);
 a[2] = ((iVal >> 40) & 0xFF);
 a[3] = ((iVal >> 32) & 0xFF);
 a[4] = ((iVal >> 24) & 0xFF);
 a[5] = ((iVal >> 16) & 0xFF);
 a[6] = ((iVal >> 8) & 0xFF);
 a[7] = ((iVal >> 0) & 0xFF);
}

/*
** Write iVal, formated as a 32-bit big-endian unsigned integer, to the
** buffer indicated by the first argument.
*/
static void fts5PutU32(u8 *a, u32 iVal){
 a[0] = ((iVal >> 24) & 0xFF);
 a[1] = ((iVal >> 16) & 0xFF);
 a[2] = ((iVal >> 8) & 0xFF);
 a[3] = ((iVal >> 0) & 0xFF);
}

/*
** Allocate and return a buffer at least nByte bytes in size.
**
** If an OOM error is encountered, return NULL and set the error code in
** the Fts5Index handle passed as the first argument.
*/
static void *fts5IdxMalloc(Fts5Index *p, sqlite3_int64 nByte){
 return sqlite3Fts5MallocZero(&p->rc, nByte);
}

/*
** Compare the contents of the pLeft buffer with the pRight/nRight blob.
**
** Return -ve if pLeft is smaller than pRight, 0 if they are equal or
** +ve if pRight is smaller than pLeft. In other words:
**
** res = *pLeft - *pRight
*/
#ifdef SQLITE_DEBUG
static int fts5BufferCompareBlob(
 Fts5Buffer *pLeft, /* Left hand side of comparison */
 const u8 *pRight, int nRight /* Right hand side of comparison */
){
 int nCmp = MIN(pLeft->n, nRight);
 int res = memcmp(pLeft->p, pRight, nCmp);
 return (res==0 ? (pLeft->n - nRight) : res);
}
#endif

/*
** Compare the contents of the two buffers using memcmp(). If one buffer
** is a prefix of the other, it is considered the lesser.
**
** Return -ve if pLeft is smaller than pRight, 0 if they are equal or
** +ve if pRight is smaller than pLeft. In other words:
**
** res = *pLeft - *pRight
*/
static int fts5BufferCompare(Fts5Buffer *pLeft, Fts5Buffer *pRight){
 int nCmp, res;
 nCmp = MIN(pLeft->n, pRight->n);
 assert( nCmp<=0 || pLeft->p!=0 );
 assert( nCmp<=0 || pRight->p!=0 );
 res = fts5Memcmp(pLeft->p, pRight->p, nCmp);
 return (res==0 ? (pLeft->n - pRight->n) : res);
}

static int fts5LeafFirstTermOff(Fts5Data *pLeaf){
 int ret;
 fts5GetVarint32(&pLeaf->p[pLeaf->szLeaf], ret);
 return ret;
}

/*
** Close the read-only blob handle, if it is open.
*/
static void sqlite3Fts5IndexCloseReader(Fts5Index *p){
 if( p->pReader ){
 sqlite3_blob *pReader = p->pReader;
 p->pReader = 0;
 sqlite3_blob_close(pReader);
 }
}

/*
** Retrieve a record from the %_data table.
**
** If an error occurs, NULL is returned and an error left in the
** Fts5Index object.
*/
static Fts5Data *fts5DataRead(Fts5Index *p, i64 iRowid){
 Fts5Data *pRet = 0;
 if( p->rc==SQLITE_OK ){
 int rc = SQLITE_OK;

 if( p->pReader ){
 /* This call may return SQLITE_ABORT if there has been a savepoint
 ** rollback since it was last used. In this case a new blob handle
 ** is required. */
 sqlite3_blob *pBlob = p->pReader;
 p->pReader = 0;
 rc = sqlite3_blob_reopen(pBlob, iRowid);
 assert( p->pReader==0 );
 p->pReader = pBlob;
 if( rc!=SQLITE_OK ){
 sqlite3Fts5IndexCloseReader(p);
 }
 if( rc==SQLITE_ABORT ) rc = SQLITE_OK;
 }

 /* If the blob handle is not open at this point, open it and seek
 ** to the requested entry. */
 if( p->pReader==0 && rc==SQLITE_OK ){
 Fts5Config *pConfig = p->pConfig;
 rc = sqlite3_blob_open(pConfig->db,
 pConfig->zDb, p->zDataTbl, "block", iRowid, 0, &p->pReader
 );
 }

 /* If either of the sqlite3_blob_open() or sqlite3_blob_reopen() calls
 ** above returned SQLITE_ERROR, return SQLITE_CORRUPT_VTAB instead.
 ** All the reasons those functions might return SQLITE_ERROR - missing
 ** table, missing row, non-blob/text in block column - indicate
 ** backing store corruption. */
 if( rc==SQLITE_ERROR ) rc = FTS5_CORRUPT;

 if( rc==SQLITE_OK ){
 u8 *aOut = 0; /* Read blob data into this buffer */
 int nByte = sqlite3_blob_bytes(p->pReader);
 int szData = (sizeof(Fts5Data) + 7) & ~7;
 sqlite3_int64 nAlloc = szData + nByte + FTS5_DATA_PADDING;
 pRet = (Fts5Data*)sqlite3_malloc64(nAlloc);
 if( pRet ){
 pRet->nn = nByte;
 aOut = pRet->p = (u8*)pRet + szData;
 }else{
 rc = SQLITE_NOMEM;
 }

 if( rc==SQLITE_OK ){
 rc = sqlite3_blob_read(p->pReader, aOut, nByte, 0);
 }
 if( rc!=SQLITE_OK ){
 sqlite3_free(pRet);
 pRet = 0;
 }else{
 /* TODO1: Fix this */
 pRet->p[nByte] = 0x00;
 pRet->p[nByte+1] = 0x00;
 pRet->szLeaf = fts5GetU16(&pRet->p[2]);
 }
 }
 p->rc = rc;
 p->nRead++;
 }

 assert( (pRet==0)==(p->rc!=SQLITE_OK) );
 assert( pRet==0 || EIGHT_BYTE_ALIGNMENT( pRet->p ) );
 return pRet;
}

/*
** Release a reference to data record returned by an earlier call to
** fts5DataRead().
*/
static void fts5DataRelease(Fts5Data *pData){
 sqlite3_free(pData);
}

static Fts5Data *fts5LeafRead(Fts5Index *p, i64 iRowid){
 Fts5Data *pRet = fts5DataRead(p, iRowid);
 if( pRet ){
 if( pRet->nn<4 || pRet->szLeaf>pRet->nn ){
 p->rc = FTS5_CORRUPT;
 fts5DataRelease(pRet);
 pRet = 0;
 }
 }
 return pRet;
}

static int fts5IndexPrepareStmt(
 Fts5Index *p,
 sqlite3_stmt **ppStmt,
 char *zSql
){
 if( p->rc==SQLITE_OK ){
 if( zSql ){
 p->rc = sqlite3_prepare_v3(p->pConfig->db, zSql, -1,
 SQLITE_PREPARE_PERSISTENT|SQLITE_PREPARE_NO_VTAB,
 ppStmt, 0);
 }else{
 p->rc = SQLITE_NOMEM;
 }
 }
 sqlite3_free(zSql);
 return p->rc;
}

/*
** INSERT OR REPLACE a record into the %_data table.
*/
static void fts5DataWrite(Fts5Index *p, i64 iRowid, const u8 *pData, int nData){
 if( p->rc!=SQLITE_OK ) return;

 if( p->pWriter==0 ){
 Fts5Config *pConfig = p->pConfig;
 fts5IndexPrepareStmt(p, &p->pWriter, sqlite3_mprintf(
 "REPLACE INTO '%q'.'%q_data'(id, block) VALUES(?,?)",
 pConfig->zDb, pConfig->zName
 ));
 if( p->rc ) return;
 }

 sqlite3_bind_int64(p->pWriter, 1, iRowid);
 sqlite3_bind_blob(p->pWriter, 2, pData, nData, SQLITE_STATIC);
 sqlite3_step(p->pWriter);
 p->rc = sqlite3_reset(p->pWriter);
 sqlite3_bind_null(p->pWriter, 2);
}

/*
** Execute the following SQL:
**
** DELETE FROM %_data WHERE id BETWEEN $iFirst AND $iLast
*/
static void fts5DataDelete(Fts5Index *p, i64 iFirst, i64 iLast){
 if( p->rc!=SQLITE_OK ) return;

 if( p->pDeleter==0 ){
 Fts5Config *pConfig = p->pConfig;
 char *zSql = sqlite3_mprintf(
 "DELETE FROM '%q'.'%q_data' WHERE id>=? AND id<=?",
 pConfig->zDb, pConfig->zName
 );
 if( fts5IndexPrepareStmt(p, &p->pDeleter, zSql) ) return;
 }

 sqlite3_bind_int64(p->pDeleter, 1, iFirst);
 sqlite3_bind_int64(p->pDeleter, 2, iLast);
 sqlite3_step(p->pDeleter);
 p->rc = sqlite3_reset(p->pDeleter);
}

/*
** Remove all records associated with segment iSegid.
*/
static void fts5DataRemoveSegment(Fts5Index *p, Fts5StructureSegment *pSeg){
 int iSegid = pSeg->iSegid;
 i64 iFirst = FTS5_SEGMENT_ROWID(iSegid, 0);
 i64 iLast = FTS5_SEGMENT_ROWID(iSegid+1, 0)-1;
 fts5DataDelete(p, iFirst, iLast);

 if( pSeg->nPgTombstone ){
 i64 iTomb1 = FTS5_TOMBSTONE_ROWID(iSegid, 0);
 i64 iTomb2 = FTS5_TOMBSTONE_ROWID(iSegid, pSeg->nPgTombstone-1);
 fts5DataDelete(p, iTomb1, iTomb2);
 }
 if( p->pIdxDeleter==0 ){
 Fts5Config *pConfig = p->pConfig;
 fts5IndexPrepareStmt(p, &p->pIdxDeleter, sqlite3_mprintf(
 "DELETE FROM '%q'.'%q_idx' WHERE segid=?",
 pConfig->zDb, pConfig->zName
 ));
 }
 if( p->rc==SQLITE_OK ){
 sqlite3_bind_int(p->pIdxDeleter, 1, iSegid);
 sqlite3_step(p->pIdxDeleter);
 p->rc = sqlite3_reset(p->pIdxDeleter);
 }
}

/*
** Release a reference to an Fts5Structure object returned by an earlier
** call to fts5StructureRead() or fts5StructureDecode().
*/
static void fts5StructureRelease(Fts5Structure *pStruct){
 if( pStruct && 0>=(--pStruct->nRef) ){
 int i;
 assert( pStruct->nRef==0 );
 for(i=0; i<pStruct->nLevel; i++){
 sqlite3_free(pStruct->aLevel[i].aSeg);
 }
 sqlite3_free(pStruct);
 }
}

static void fts5StructureRef(Fts5Structure *pStruct){
 pStruct->nRef++;
}

static void *sqlite3Fts5StructureRef(Fts5Index *p){
 fts5StructureRef(p->pStruct);
 return (void*)p->pStruct;
}
static void sqlite3Fts5StructureRelease(void *p){
 if( p ){
 fts5StructureRelease((Fts5Structure*)p);
 }
}
static int sqlite3Fts5StructureTest(Fts5Index *p, void *pStruct){
 if( p->pStruct!=(Fts5Structure*)pStruct ){
 return SQLITE_ABORT;
 }
 return SQLITE_OK;
}

/*
** Ensure that structure object (*pp) is writable.
**
** This function is a no-op if (*pRc) is not SQLITE_OK when it is called. If
** an error occurs, (*pRc) is set to an SQLite error code before returning.
*/
static void fts5StructureMakeWritable(int *pRc, Fts5Structure **pp){
 Fts5Structure *p = *pp;
 if( *pRc==SQLITE_OK && p->nRef>1 ){
 i64 nByte = sizeof(Fts5Structure)+(p->nLevel-1)*sizeof(Fts5StructureLevel);
 Fts5Structure *pNew;
 pNew = (Fts5Structure*)sqlite3Fts5MallocZero(pRc, nByte);
 if( pNew ){
 int i;
 memcpy(pNew, p, nByte);
 for(i=0; i<p->nLevel; i++) pNew->aLevel[i].aSeg = 0;
 for(i=0; i<p->nLevel; i++){
 Fts5StructureLevel *pLvl = &pNew->aLevel[i];
 nByte = sizeof(Fts5StructureSegment) * pNew->aLevel[i].nSeg;
 pLvl->aSeg = (Fts5StructureSegment*)sqlite3Fts5MallocZero(pRc, nByte);
 if( pLvl->aSeg==0 ){
 for(i=0; i<p->nLevel; i++){
 sqlite3_free(pNew->aLevel[i].aSeg);
 }
 sqlite3_free(pNew);
 return;
 }
 memcpy(pLvl->aSeg, p->aLevel[i].aSeg, nByte);
 }
 p->nRef--;
 pNew->nRef = 1;
 }
 *pp = pNew;
 }
}

/*
** Deserialize and return the structure record currently stored in serialized
** form within buffer pData/nData.
**
** The Fts5Structure.aLevel[] and each Fts5StructureLevel.aSeg[] array
** are over-allocated by one slot. This allows the structure contents
** to be more easily edited.
**
** If an error occurs, *ppOut is set to NULL and an SQLite error code
** returned. Otherwise, *ppOut is set to point to the new object and
** SQLITE_OK returned.
*/
static int fts5StructureDecode(
 const u8 *pData, /* Buffer containing serialized structure */
 int nData, /* Size of buffer pData in bytes */
 int *piCookie, /* Configuration cookie value */
 Fts5Structure **ppOut /* OUT: Deserialized object */
){
 int rc = SQLITE_OK;
 int i = 0;
 int iLvl;
 int nLevel = 0;
 int nSegment = 0;
 sqlite3_int64 nByte; /* Bytes of space to allocate at pRet */
 Fts5Structure *pRet = 0; /* Structure object to return */
 int bStructureV2 = 0; /* True for FTS5_STRUCTURE_V2 */
 u64 nOriginCntr = 0; /* Largest origin value seen so far */

 /* Grab the cookie value */
 if( piCookie ) *piCookie = sqlite3Fts5Get32(pData);
 i = 4;

 /* Check if this is a V2 structure record. Set bStructureV2 if it is. */
 if( 0==memcmp(&pData[i], FTS5_STRUCTURE_V2, 4) ){
 i += 4;
 bStructureV2 = 1;
 }

 /* Read the total number of levels and segments from the start of the
 ** structure record. */
 i += fts5GetVarint32(&pData[i], nLevel);
 i += fts5GetVarint32(&pData[i], nSegment);
 if( nLevel>FTS5_MAX_SEGMENT || nLevel<0
 || nSegment>FTS5_MAX_SEGMENT || nSegment<0
 ){
 return FTS5_CORRUPT;
 }
 nByte = (
 sizeof(Fts5Structure) + /* Main structure */
 sizeof(Fts5StructureLevel) * (nLevel-1) /* aLevel[] array */
 );
 pRet = (Fts5Structure*)sqlite3Fts5MallocZero(&rc, nByte);

 if( pRet ){
 pRet->nRef = 1;
 pRet->nLevel = nLevel;
 pRet->nSegment = nSegment;
 i += sqlite3Fts5GetVarint(&pData[i], &pRet->nWriteCounter);

 for(iLvl=0; rc==SQLITE_OK && iLvl<nLevel; iLvl++){
 Fts5StructureLevel *pLvl = &pRet->aLevel[iLvl];
 int nTotal = 0;
 int iSeg;

 if( i>=nData ){
 rc = FTS5_CORRUPT;
 }else{
 i += fts5GetVarint32(&pData[i], pLvl->nMerge);
 i += fts5GetVarint32(&pData[i], nTotal);
 if( nTotal<pLvl->nMerge ) rc = FTS5_CORRUPT;
 pLvl->aSeg = (Fts5StructureSegment*)sqlite3Fts5MallocZero(&rc,
 nTotal * sizeof(Fts5StructureSegment)
 );
 nSegment -= nTotal;
 }

 if( rc==SQLITE_OK ){
 pLvl->nSeg = nTotal;
 for(iSeg=0; iSeg<nTotal; iSeg++){
 Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
 if( i>=nData ){
 rc = FTS5_CORRUPT;
 break;
 }
 assert( pSeg!=0 );
 i += fts5GetVarint32(&pData[i], pSeg->iSegid);
 i += fts5GetVarint32(&pData[i], pSeg->pgnoFirst);
 i += fts5GetVarint32(&pData[i], pSeg->pgnoLast);
 if( bStructureV2 ){
 i += fts5GetVarint(&pData[i], &pSeg->iOrigin1);
 i += fts5GetVarint(&pData[i], &pSeg->iOrigin2);
 i += fts5GetVarint32(&pData[i], pSeg->nPgTombstone);
 i += fts5GetVarint(&pData[i], &pSeg->nEntryTombstone);
 i += fts5GetVarint(&pData[i], &pSeg->nEntry);
 nOriginCntr = MAX(nOriginCntr, pSeg->iOrigin2);
 }
 if( pSeg->pgnoLast<pSeg->pgnoFirst ){
 rc = FTS5_CORRUPT;
 break;
 }
 }
 if( iLvl>0 && pLvl[-1].nMerge && nTotal==0 ) rc = FTS5_CORRUPT;
 if( iLvl==nLevel-1 && pLvl->nMerge ) rc = FTS5_CORRUPT;
 }
 }
 if( nSegment!=0 && rc==SQLITE_OK ) rc = FTS5_CORRUPT;
 if( bStructureV2 ){
 pRet->nOriginCntr = nOriginCntr+1;
 }

 if( rc!=SQLITE_OK ){
 fts5StructureRelease(pRet);
 pRet = 0;
 }
 }

 *ppOut = pRet;
 return rc;
}

/*
** Add a level to the Fts5Structure.aLevel[] array of structure object
** (*ppStruct).
*/
static void fts5StructureAddLevel(int *pRc, Fts5Structure **ppStruct){
 fts5StructureMakeWritable(pRc, ppStruct);
 assert( (ppStruct!=0 && (*ppStruct)!=0) || (*pRc)!=SQLITE_OK );
 if( *pRc==SQLITE_OK ){
 Fts5Structure *pStruct = *ppStruct;
 int nLevel = pStruct->nLevel;
 sqlite3_int64 nByte = (
 sizeof(Fts5Structure) + /* Main structure */
 sizeof(Fts5StructureLevel) * (nLevel+1) /* aLevel[] array */
 );

 pStruct = sqlite3_realloc64(pStruct, nByte);
 if( pStruct ){
 memset(&pStruct->aLevel[nLevel], 0, sizeof(Fts5StructureLevel));
 pStruct->nLevel++;
 *ppStruct = pStruct;
 }else{
 *pRc = SQLITE_NOMEM;
 }
 }
}

/*
** Extend level iLvl so that there is room for at least nExtra more
** segments.
*/
static void fts5StructureExtendLevel(
 int *pRc,
 Fts5Structure *pStruct,
 int iLvl,
 int nExtra,
 int bInsert
){
 if( *pRc==SQLITE_OK ){
 Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
 Fts5StructureSegment *aNew;
 sqlite3_int64 nByte;

 nByte = (pLvl->nSeg + nExtra) * sizeof(Fts5StructureSegment);
 aNew = sqlite3_realloc64(pLvl->aSeg, nByte);
 if( aNew ){
 if( bInsert==0 ){
 memset(&aNew[pLvl->nSeg], 0, sizeof(Fts5StructureSegment) * nExtra);
 }else{
 int nMove = pLvl->nSeg * sizeof(Fts5StructureSegment);
 memmove(&aNew[nExtra], aNew, nMove);
 memset(aNew, 0, sizeof(Fts5StructureSegment) * nExtra);
 }
 pLvl->aSeg = aNew;
 }else{
 *pRc = SQLITE_NOMEM;
 }
 }
}

static Fts5Structure *fts5StructureReadUncached(Fts5Index *p){
 Fts5Structure *pRet = 0;
 Fts5Config *pConfig = p->pConfig;
 int iCookie; /* Configuration cookie */
 Fts5Data *pData;

 pData = fts5DataRead(p, FTS5_STRUCTURE_ROWID);
 if( p->rc==SQLITE_OK ){
 /* TODO: Do we need this if the leaf-index is appended? Probably... */
 memset(&pData->p[pData->nn], 0, FTS5_DATA_PADDING);
 p->rc = fts5StructureDecode(pData->p, pData->nn, &iCookie, &pRet);
 if( p->rc==SQLITE_OK && (pConfig->pgsz==0 || pConfig->iCookie!=iCookie) ){
 p->rc = sqlite3Fts5ConfigLoad(pConfig, iCookie);
 }
 fts5DataRelease(pData);
 if( p->rc!=SQLITE_OK ){
 fts5StructureRelease(pRet);
 pRet = 0;
 }
 }

 return pRet;
}

static i64 fts5IndexDataVersion(Fts5Index *p){
 i64 iVersion = 0;

 if( p->rc==SQLITE_OK ){
 if( p->pDataVersion==0 ){
 p->rc = fts5IndexPrepareStmt(p, &p->pDataVersion,
 sqlite3_mprintf("PRAGMA %Q.data_version", p->pConfig->zDb)
 );
 if( p->rc ) return 0;
 }

 if( SQLITE_ROW==sqlite3_step(p->pDataVersion) ){
 iVersion = sqlite3_column_int64(p->pDataVersion, 0);
 }
 p->rc = sqlite3_reset(p->pDataVersion);
 }

 return iVersion;
}

/*
** Read, deserialize and return the structure record.
**
** The Fts5Structure.aLevel[] and each Fts5StructureLevel.aSeg[] array
** are over-allocated as described for function fts5StructureDecode()
** above.
**
** If an error occurs, NULL is returned and an error code left in the
** Fts5Index handle. If an error has already occurred when this function
** is called, it is a no-op.
*/
static Fts5Structure *fts5StructureRead(Fts5Index *p){

 if( p->pStruct==0 ){
 p->iStructVersion = fts5IndexDataVersion(p);
 if( p->rc==SQLITE_OK ){
 p->pStruct = fts5StructureReadUncached(p);
 }
 }

#if 0
 else{
 Fts5Structure *pTest = fts5StructureReadUncached(p);
 if( pTest ){
 int i, j;
 assert_nc( p->pStruct->nSegment==pTest->nSegment );
 assert_nc( p->pStruct->nLevel==pTest->nLevel );
 for(i=0; i<pTest->nLevel; i++){
 assert_nc( p->pStruct->aLevel[i].nMerge==pTest->aLevel[i].nMerge );
 assert_nc( p->pStruct->aLevel[i].nSeg==pTest->aLevel[i].nSeg );
 for(j=0; j<pTest->aLevel[i].nSeg; j++){
 Fts5StructureSegment *p1 = &pTest->aLevel[i].aSeg[j];
 Fts5StructureSegment *p2 = &p->pStruct->aLevel[i].aSeg[j];
 assert_nc( p1->iSegid==p2->iSegid );
 assert_nc( p1->pgnoFirst==p2->pgnoFirst );
 assert_nc( p1->pgnoLast==p2->pgnoLast );
 }
 }
 fts5StructureRelease(pTest);
 }
 }
#endif

 if( p->rc!=SQLITE_OK ) return 0;
 assert( p->iStructVersion!=0 );
 assert( p->pStruct!=0 );
 fts5StructureRef(p->pStruct);
 return p->pStruct;
}

static void fts5StructureInvalidate(Fts5Index *p){
 if( p->pStruct ){
 fts5StructureRelease(p->pStruct);
 p->pStruct = 0;
 }
}

/*
** Return the total number of segments in index structure pStruct. This
** function is only ever used as part of assert() conditions.
*/
#ifdef SQLITE_DEBUG
static int fts5StructureCountSegments(Fts5Structure *pStruct){
 int nSegment = 0; /* Total number of segments */
 if( pStruct ){
 int iLvl; /* Used to iterate through levels */
 for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
 nSegment += pStruct->aLevel[iLvl].nSeg;
 }
 }

 return nSegment;
}
#endif

#define fts5BufferSafeAppendBlob(pBuf, pBlob, nBlob) { \
 assert( (pBuf)->nSpace>=((pBuf)->n+nBlob) ); \
 memcpy(&(pBuf)->p[(pBuf)->n], pBlob, nBlob); \
 (pBuf)->n += nBlob; \
}

#define fts5BufferSafeAppendVarint(pBuf, iVal) { \
 (pBuf)->n += sqlite3Fts5PutVarint(&(pBuf)->p[(pBuf)->n], (iVal)); \
 assert( (pBuf)->nSpace>=(pBuf)->n ); \
}

/*
** Serialize and store the "structure" record.
**
** If an error occurs, leave an error code in the Fts5Index object. If an
** error has already occurred, this function is a no-op.
*/
static void fts5StructureWrite(Fts5Index *p, Fts5Structure *pStruct){
 if( p->rc==SQLITE_OK ){
 Fts5Buffer buf; /* Buffer to serialize record into */
 int iLvl; /* Used to iterate through levels */
 int iCookie; /* Cookie value to store */
 int nHdr = (pStruct->nOriginCntr>0 ? (4+4+9+9+9) : (4+9+9));

 assert( pStruct->nSegment==fts5StructureCountSegments(pStruct) );
 memset(&buf, 0, sizeof(Fts5Buffer));

 /* Append the current configuration cookie */
 iCookie = p->pConfig->iCookie;
 if( iCookie<0 ) iCookie = 0;

 if( 0==sqlite3Fts5BufferSize(&p->rc, &buf, nHdr) ){
 sqlite3Fts5Put32(buf.p, iCookie);
 buf.n = 4;
 if( pStruct->nOriginCntr>0 ){
 fts5BufferSafeAppendBlob(&buf, FTS5_STRUCTURE_V2, 4);
 }
 fts5BufferSafeAppendVarint(&buf, pStruct->nLevel);
 fts5BufferSafeAppendVarint(&buf, pStruct->nSegment);
 fts5BufferSafeAppendVarint(&buf, (i64)pStruct->nWriteCounter);
 }

 for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
 int iSeg; /* Used to iterate through segments */
 Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
 fts5BufferAppendVarint(&p->rc, &buf, pLvl->nMerge);
 fts5BufferAppendVarint(&p->rc, &buf, pLvl->nSeg);
 assert( pLvl->nMerge<=pLvl->nSeg );

 for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
 Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->iSegid);
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->pgnoFirst);
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->pgnoLast);
 if( pStruct->nOriginCntr>0 ){
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->iOrigin1);
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->iOrigin2);
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->nPgTombstone);
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->nEntryTombstone);
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->nEntry);
 }
 }
 }

 fts5DataWrite(p, FTS5_STRUCTURE_ROWID, buf.p, buf.n);
 fts5BufferFree(&buf);
 }
}

#if 0
static void fts5DebugStructure(int*,Fts5Buffer*,Fts5Structure*);
static void fts5PrintStructure(const char *zCaption, Fts5Structure *pStruct){
 int rc = SQLITE_OK;
 Fts5Buffer buf;
 memset(&buf, 0, sizeof(buf));
 fts5DebugStructure(&rc, &buf, pStruct);
 fprintf(stdout, "%s: %s\n", zCaption, buf.p);
 fflush(stdout);
 fts5BufferFree(&buf);
}
#else
# define fts5PrintStructure(x,y)
#endif

static int fts5SegmentSize(Fts5StructureSegment *pSeg){
 return 1 + pSeg->pgnoLast - pSeg->pgnoFirst;
}

/*
** Return a copy of index structure pStruct. Except, promote as many
** segments as possible to level iPromote. If an OOM occurs, NULL is
** returned.
*/
static void fts5StructurePromoteTo(
 Fts5Index *p,
 int iPromote,
 int szPromote,
 Fts5Structure *pStruct
){
 int il, is;
 Fts5StructureLevel *pOut = &pStruct->aLevel[iPromote];

 if( pOut->nMerge==0 ){
 for(il=iPromote+1; il<pStruct->nLevel; il++){
 Fts5StructureLevel *pLvl = &pStruct->aLevel[il];
 if( pLvl->nMerge ) return;
 for(is=pLvl->nSeg-1; is>=0; is--){
 int sz = fts5SegmentSize(&pLvl->aSeg[is]);
 if( sz>szPromote ) return;
 fts5StructureExtendLevel(&p->rc, pStruct, iPromote, 1, 1);
 if( p->rc ) return;
 memcpy(pOut->aSeg, &pLvl->aSeg[is], sizeof(Fts5StructureSegment));
 pOut->nSeg++;
 pLvl->nSeg--;
 }
 }
 }
}

/*
** A new segment has just been written to level iLvl of index structure
** pStruct. This function determines if any segments should be promoted
** as a result. Segments are promoted in two scenarios:
**
** a) If the segment just written is smaller than one or more segments
** within the previous populated level, it is promoted to the previous
** populated level.
**
** b) If the segment just written is larger than the newest segment on
** the next populated level, then that segment, and any other adjacent
** segments that are also smaller than the one just written, are
** promoted.
**
** If one or more segments are promoted, the structure object is updated
** to reflect this.
*/
static void fts5StructurePromote(
 Fts5Index *p, /* FTS5 backend object */
 int iLvl, /* Index level just updated */
 Fts5Structure *pStruct /* Index structure */
){
 if( p->rc==SQLITE_OK ){
 int iTst;
 int iPromote = -1;
 int szPromote = 0; /* Promote anything this size or smaller */
 Fts5StructureSegment *pSeg; /* Segment just written */
 int szSeg; /* Size of segment just written */
 int nSeg = pStruct->aLevel[iLvl].nSeg;

 if( nSeg==0 ) return;
 pSeg = &pStruct->aLevel[iLvl].aSeg[pStruct->aLevel[iLvl].nSeg-1];
 szSeg = (1 + pSeg->pgnoLast - pSeg->pgnoFirst);

 /* Check for condition (a) */
 for(iTst=iLvl-1; iTst>=0 && pStruct->aLevel[iTst].nSeg==0; iTst--);
 if( iTst>=0 ){
 int i;
 int szMax = 0;
 Fts5StructureLevel *pTst = &pStruct->aLevel[iTst];
 assert( pTst->nMerge==0 );
 for(i=0; i<pTst->nSeg; i++){
 int sz = pTst->aSeg[i].pgnoLast - pTst->aSeg[i].pgnoFirst + 1;
 if( sz>szMax ) szMax = sz;
 }
 if( szMax>=szSeg ){
 /* Condition (a) is true. Promote the newest segment on level
 ** iLvl to level iTst. */
 iPromote = iTst;
 szPromote = szMax;
 }
 }

 /* If condition (a) is not met, assume (b) is true. StructurePromoteTo()
 ** is a no-op if it is not. */
 if( iPromote<0 ){
 iPromote = iLvl;
 szPromote = szSeg;
 }
 fts5StructurePromoteTo(p, iPromote, szPromote, pStruct);
 }
}

/*
** Advance the iterator passed as the only argument. If the end of the
** doclist-index page is reached, return non-zero.
*/
static int fts5DlidxLvlNext(Fts5DlidxLvl *pLvl){
 Fts5Data *pData = pLvl->pData;

 if( pLvl->iOff==0 ){
 assert( pLvl->bEof==0 );
 pLvl->iOff = 1;
 pLvl->iOff += fts5GetVarint32(&pData->p[1], pLvl->iLeafPgno);
 pLvl->iOff += fts5GetVarint(&pData->p[pLvl->iOff], (u64*)&pLvl->iRowid);
 pLvl->iFirstOff = pLvl->iOff;
 }else{
 int iOff;
 for(iOff=pLvl->iOff; iOff<pData->nn; iOff++){
 if( pData->p[iOff] ) break;
 }

 if( iOff<pData->nn ){
 u64 iVal;
 pLvl->iLeafPgno += (iOff - pLvl->iOff) + 1;
 iOff += fts5GetVarint(&pData->p[iOff], &iVal);
 pLvl->iRowid += iVal;
 pLvl->iOff = iOff;
 }else{
 pLvl->bEof = 1;
 }
 }

 return pLvl->bEof;
}

/*
** Advance the iterator passed as the only argument.
*/
static int fts5DlidxIterNextR(Fts5Index *p, Fts5DlidxIter *pIter, int iLvl){
 Fts5DlidxLvl *pLvl = &pIter->aLvl[iLvl];

 assert( iLvl<pIter->nLvl );
 if( fts5DlidxLvlNext(pLvl) ){
 if( (iLvl+1) < pIter->nLvl ){
 fts5DlidxIterNextR(p, pIter, iLvl+1);
 if( pLvl[1].bEof==0 ){
 fts5DataRelease(pLvl->pData);
 memset(pLvl, 0, sizeof(Fts5DlidxLvl));
 pLvl->pData = fts5DataRead(p,
 FTS5_DLIDX_ROWID(pIter->iSegid, iLvl, pLvl[1].iLeafPgno)
 );
 if( pLvl->pData ) fts5DlidxLvlNext(pLvl);
 }
 }
 }

 return pIter->aLvl[0].bEof;
}
static int fts5DlidxIterNext(Fts5Index *p, Fts5DlidxIter *pIter){
 return fts5DlidxIterNextR(p, pIter, 0);
}

/*
** The iterator passed as the first argument has the following fields set
** as follows. This function sets up the rest of the iterator so that it
** points to the first rowid in the doclist-index.
**
** pData:
** pointer to doclist-index record,
**
** When this function is called pIter->iLeafPgno is the page number the
** doclist is associated with (the one featuring the term).
*/
static int fts5DlidxIterFirst(Fts5DlidxIter *pIter){
 int i;
 for(i=0; i<pIter->nLvl; i++){
 fts5DlidxLvlNext(&pIter->aLvl[i]);
 }
 return pIter->aLvl[0].bEof;
}

static int fts5DlidxIterEof(Fts5Index *p, Fts5DlidxIter *pIter){
 return p->rc!=SQLITE_OK || pIter->aLvl[0].bEof;
}

static void fts5DlidxIterLast(Fts5Index *p, Fts5DlidxIter *pIter){
 int i;

 /* Advance each level to the last entry on the last page */
 for(i=pIter->nLvl-1; p->rc==SQLITE_OK && i>=0; i--){
 Fts5DlidxLvl *pLvl = &pIter->aLvl[i];
 while( fts5DlidxLvlNext(pLvl)==0 );
 pLvl->bEof = 0;

 if( i>0 ){
 Fts5DlidxLvl *pChild = &pLvl[-1];
 fts5DataRelease(pChild->pData);
 memset(pChild, 0, sizeof(Fts5DlidxLvl));
 pChild->pData = fts5DataRead(p,
 FTS5_DLIDX_ROWID(pIter->iSegid, i-1, pLvl->iLeafPgno)
 );
 }
 }
}

/*
** Move the iterator passed as the only argument to the previous entry.
*/
static int fts5DlidxLvlPrev(Fts5DlidxLvl *pLvl){
 int iOff = pLvl->iOff;

 assert( pLvl->bEof==0 );
 if( iOff<=pLvl->iFirstOff ){
 pLvl->bEof = 1;
 }else{
 u8 *a = pLvl->pData->p;

 pLvl->iOff = 0;
 fts5DlidxLvlNext(pLvl);
 while( 1 ){
 int nZero = 0;
 int ii = pLvl->iOff;
 u64 delta = 0;

 while( a[ii]==0 ){
 nZero++;
 ii++;
 }
 ii += sqlite3Fts5GetVarint(&a[ii], &delta);

 if( ii>=iOff ) break;
 pLvl->iLeafPgno += nZero+1;
 pLvl->iRowid += delta;
 pLvl->iOff = ii;
 }
 }

 return pLvl->bEof;
}

static int fts5DlidxIterPrevR(Fts5Index *p, Fts5DlidxIter *pIter, int iLvl){
 Fts5DlidxLvl *pLvl = &pIter->aLvl[iLvl];

 assert( iLvl<pIter->nLvl );
 if( fts5DlidxLvlPrev(pLvl) ){
 if( (iLvl+1) < pIter->nLvl ){
 fts5DlidxIterPrevR(p, pIter, iLvl+1);
 if( pLvl[1].bEof==0 ){
 fts5DataRelease(pLvl->pData);
 memset(pLvl, 0, sizeof(Fts5DlidxLvl));
 pLvl->pData = fts5DataRead(p,
 FTS5_DLIDX_ROWID(pIter->iSegid, iLvl, pLvl[1].iLeafPgno)
 );
 if( pLvl->pData ){
 while( fts5DlidxLvlNext(pLvl)==0 );
 pLvl->bEof = 0;
 }
 }
 }
 }

 return pIter->aLvl[0].bEof;
}
static int fts5DlidxIterPrev(Fts5Index *p, Fts5DlidxIter *pIter){
 return fts5DlidxIterPrevR(p, pIter, 0);
}

/*
** Free a doclist-index iterator object allocated by fts5DlidxIterInit().
*/
static void fts5DlidxIterFree(Fts5DlidxIter *pIter){
 if( pIter ){
 int i;
 for(i=0; i<pIter->nLvl; i++){
 fts5DataRelease(pIter->aLvl[i].pData);
 }
 sqlite3_free(pIter);
 }
}

static Fts5DlidxIter *fts5DlidxIterInit(
 Fts5Index *p, /* Fts5 Backend to iterate within */
 int bRev, /* True for ORDER BY ASC */
 int iSegid, /* Segment id */
 int iLeafPg /* Leaf page number to load dlidx for */
){
 Fts5DlidxIter *pIter = 0;
 int i;
 int bDone = 0;

 for(i=0; p->rc==SQLITE_OK && bDone==0; i++){
 sqlite3_int64 nByte = sizeof(Fts5DlidxIter) + i * sizeof(Fts5DlidxLvl);
 Fts5DlidxIter *pNew;

 pNew = (Fts5DlidxIter*)sqlite3_realloc64(pIter, nByte);
 if( pNew==0 ){
 p->rc = SQLITE_NOMEM;
 }else{
 i64 iRowid = FTS5_DLIDX_ROWID(iSegid, i, iLeafPg);
 Fts5DlidxLvl *pLvl = &pNew->aLvl[i];
 pIter = pNew;
 memset(pLvl, 0, sizeof(Fts5DlidxLvl));
 pLvl->pData = fts5DataRead(p, iRowid);
 if( pLvl->pData && (pLvl->pData->p[0] & 0x0001)==0 ){
 bDone = 1;
 }
 pIter->nLvl = i+1;
 }
 }

 if( p->rc==SQLITE_OK ){
 pIter->iSegid = iSegid;
 if( bRev==0 ){
 fts5DlidxIterFirst(pIter);
 }else{
 fts5DlidxIterLast(p, pIter);
 }
 }

 if( p->rc!=SQLITE_OK ){
 fts5DlidxIterFree(pIter);
 pIter = 0;
 }

 return pIter;
}

static i64 fts5DlidxIterRowid(Fts5DlidxIter *pIter){
 return pIter->aLvl[0].iRowid;
}
static int fts5DlidxIterPgno(Fts5DlidxIter *pIter){
 return pIter->aLvl[0].iLeafPgno;
}

/*
** Load the next leaf page into the segment iterator.
*/
static void fts5SegIterNextPage(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegIter *pIter /* Iterator to advance to next page */
){
 Fts5Data *pLeaf;
 Fts5StructureSegment *pSeg = pIter->pSeg;
 fts5DataRelease(pIter->pLeaf);
 pIter->iLeafPgno++;
 if( pIter->pNextLeaf ){
 pIter->pLeaf = pIter->pNextLeaf;
 pIter->pNextLeaf = 0;
 }else if( pIter->iLeafPgno<=pSeg->pgnoLast ){
 pIter->pLeaf = fts5LeafRead(p,
 FTS5_SEGMENT_ROWID(pSeg->iSegid, pIter->iLeafPgno)
 );
 }else{
 pIter->pLeaf = 0;
 }
 pLeaf = pIter->pLeaf;

 if( pLeaf ){
 pIter->iPgidxOff = pLeaf->szLeaf;
 if( fts5LeafIsTermless(pLeaf) ){
 pIter->iEndofDoclist = pLeaf->nn+1;
 }else{
 pIter->iPgidxOff += fts5GetVarint32(&pLeaf->p[pIter->iPgidxOff],
 pIter->iEndofDoclist
 );
 }
 }
}

/*
** Argument p points to a buffer containing a varint to be interpreted as a
** position list size field. Read the varint and return the number of bytes
** read. Before returning, set *pnSz to the number of bytes in the position
** list, and *pbDel to true if the delete flag is set, or false otherwise.
*/
static int fts5GetPoslistSize(const u8 *p, int *pnSz, int *pbDel){
 int nSz;
 int n = 0;
 fts5FastGetVarint32(p, n, nSz);
 assert_nc( nSz>=0 );
 *pnSz = nSz/2;
 *pbDel = nSz & 0x0001;
 return n;
}

/*
** Fts5SegIter.iLeafOffset currently points to the first byte of a
** position-list size field. Read the value of the field and store it
** in the following variables:
**
** Fts5SegIter.nPos
** Fts5SegIter.bDel
**
** Leave Fts5SegIter.iLeafOffset pointing to the first byte of the
** position list content (if any).
*/
static void fts5SegIterLoadNPos(Fts5Index *p, Fts5SegIter *pIter){
 if( p->rc==SQLITE_OK ){
 int iOff = pIter->iLeafOffset; /* Offset to read at */
 ASSERT_SZLEAF_OK(pIter->pLeaf);
 if( p->pConfig->eDetail==FTS5_DETAIL_NONE ){
 int iEod = MIN(pIter->iEndofDoclist, pIter->pLeaf->szLeaf);
 pIter->bDel = 0;
 pIter->nPos = 1;
 if( iOff<iEod && pIter->pLeaf->p[iOff]==0 ){
 pIter->bDel = 1;
 iOff++;
 if( iOff<iEod && pIter->pLeaf->p[iOff]==0 ){
 pIter->nPos = 1;
 iOff++;
 }else{
 pIter->nPos = 0;
 }
 }
 }else{
 int nSz;
 fts5FastGetVarint32(pIter->pLeaf->p, iOff, nSz);
 pIter->bDel = (nSz & 0x0001);
 pIter->nPos = nSz>>1;
 assert_nc( pIter->nPos>=0 );
 }
 pIter->iLeafOffset = iOff;
 }
}

static void fts5SegIterLoadRowid(Fts5Index *p, Fts5SegIter *pIter){
 u8 *a = pIter->pLeaf->p; /* Buffer to read data from */
 i64 iOff = pIter->iLeafOffset;

 ASSERT_SZLEAF_OK(pIter->pLeaf);
 while( iOff>=pIter->pLeaf->szLeaf ){
 fts5SegIterNextPage(p, pIter);
 if( pIter->pLeaf==0 ){
 if( p->rc==SQLITE_OK ) p->rc = FTS5_CORRUPT;
 return;
 }
 iOff = 4;
 a = pIter->pLeaf->p;
 }
 iOff += sqlite3Fts5GetVarint(&a[iOff], (u64*)&pIter->iRowid);
 pIter->iLeafOffset = iOff;
}

/*
** Fts5SegIter.iLeafOffset currently points to the first byte of the
** "nSuffix" field of a term. Function parameter nKeep contains the value
** of the "nPrefix" field (if there was one - it is passed 0 if this is
** the first term in the segment).
**
** This function populates:
**
** Fts5SegIter.term
** Fts5SegIter.rowid
**
** accordingly and leaves (Fts5SegIter.iLeafOffset) set to the content of
** the first position list. The position list belonging to document
** (Fts5SegIter.iRowid).
*/
static void fts5SegIterLoadTerm(Fts5Index *p, Fts5SegIter *pIter, int nKeep){
 u8 *a = pIter->pLeaf->p; /* Buffer to read data from */
 i64 iOff = pIter->iLeafOffset; /* Offset to read at */
 int nNew; /* Bytes of new data */

 iOff += fts5GetVarint32(&a[iOff], nNew);
 if( iOff+nNew>pIter->pLeaf->szLeaf || nKeep>pIter->term.n || nNew==0 ){
 p->rc = FTS5_CORRUPT;
 return;
 }
 pIter->term.n = nKeep;
 fts5BufferAppendBlob(&p->rc, &pIter->term, nNew, &a[iOff]);
 assert( pIter->term.n<=pIter->term.nSpace );
 iOff += nNew;
 pIter->iTermLeafOffset = iOff;
 pIter->iTermLeafPgno = pIter->iLeafPgno;
 pIter->iLeafOffset = iOff;

 if( pIter->iPgidxOff>=pIter->pLeaf->nn ){
 pIter->iEndofDoclist = pIter->pLeaf->nn+1;
 }else{
 int nExtra;
 pIter->iPgidxOff += fts5GetVarint32(&a[pIter->iPgidxOff], nExtra);
 pIter->iEndofDoclist += nExtra;
 }

 fts5SegIterLoadRowid(p, pIter);
}

static void fts5SegIterNext(Fts5Index*, Fts5SegIter*, int*);
static void fts5SegIterNext_Reverse(Fts5Index*, Fts5SegIter*, int*);
static void fts5SegIterNext_None(Fts5Index*, Fts5SegIter*, int*);

static void fts5SegIterSetNext(Fts5Index *p, Fts5SegIter *pIter){
 if( pIter->flags & FTS5_SEGITER_REVERSE ){
 pIter->xNext = fts5SegIterNext_Reverse;
 }else if( p->pConfig->eDetail==FTS5_DETAIL_NONE ){
 pIter->xNext = fts5SegIterNext_None;
 }else{
 pIter->xNext = fts5SegIterNext;
 }
}

/*
** Allocate a tombstone hash page array object (pIter->pTombArray) for
** the iterator passed as the second argument. If an OOM error occurs,
** leave an error in the Fts5Index object.
*/
static void fts5SegIterAllocTombstone(Fts5Index *p, Fts5SegIter *pIter){
 const int nTomb = pIter->pSeg->nPgTombstone;
 if( nTomb>0 ){
 int nByte = nTomb * sizeof(Fts5Data*) + sizeof(Fts5TombstoneArray);
 Fts5TombstoneArray *pNew;
 pNew = (Fts5TombstoneArray*)sqlite3Fts5MallocZero(&p->rc, nByte);
 if( pNew ){
 pNew->nTombstone = nTomb;
 pNew->nRef = 1;
 pIter->pTombArray = pNew;
 }
 }
}

/*
** Initialize the iterator object pIter to iterate through the entries in
** segment pSeg. The iterator is left pointing to the first entry when
** this function returns.
**
** If an error occurs, Fts5Index.rc is set to an appropriate error code. If
** an error has already occurred when this function is called, it is a no-op.
*/
static void fts5SegIterInit(
 Fts5Index *p, /* FTS index object */
 Fts5StructureSegment *pSeg, /* Description of segment */
 Fts5SegIter *pIter /* Object to populate */
){
 if( pSeg->pgnoFirst==0 ){
 /* This happens if the segment is being used as an input to an incremental
 ** merge and all data has already been "trimmed". See function
 ** fts5TrimSegments() for details. In this case leave the iterator empty.
 ** The caller will see the (pIter->pLeaf==0) and assume the iterator is
 ** at EOF already. */
 assert( pIter->pLeaf==0 );
 return;
 }

 if( p->rc==SQLITE_OK ){
 memset(pIter, 0, sizeof(*pIter));
 fts5SegIterSetNext(p, pIter);
 pIter->pSeg = pSeg;
 pIter->iLeafPgno = pSeg->pgnoFirst-1;
 do {
 fts5SegIterNextPage(p, pIter);
 }while( p->rc==SQLITE_OK && pIter->pLeaf && pIter->pLeaf->nn==4 );
 }

 if( p->rc==SQLITE_OK && pIter->pLeaf ){
 pIter->iLeafOffset = 4;
 assert( pIter->pLeaf!=0 );
 assert_nc( pIter->pLeaf->nn>4 );
 assert_nc( fts5LeafFirstTermOff(pIter->pLeaf)==4 );
 pIter->iPgidxOff = pIter->pLeaf->szLeaf+1;
 fts5SegIterLoadTerm(p, pIter, 0);
 fts5SegIterLoadNPos(p, pIter);
 fts5SegIterAllocTombstone(p, pIter);
 }
}

/*
** This function is only ever called on iterators created by calls to
** Fts5IndexQuery() with the FTS5INDEX_QUERY_DESC flag set.
**
** The iterator is in an unusual state when this function is called: the
** Fts5SegIter.iLeafOffset variable is set to the offset of the start of
** the position-list size field for the first relevant rowid on the page.
** Fts5SegIter.rowid is set, but nPos and bDel are not.
**
** This function advances the iterator so that it points to the last
** relevant rowid on the page and, if necessary, initializes the
** aRowidOffset[] and iRowidOffset variables. At this point the iterator
** is in its regular state - Fts5SegIter.iLeafOffset points to the first
** byte of the position list content associated with said rowid.
*/
static void fts5SegIterReverseInitPage(Fts5Index *p, Fts5SegIter *pIter){
 int eDetail = p->pConfig->eDetail;
 int n = pIter->pLeaf->szLeaf;
 int i = pIter->iLeafOffset;
 u8 *a = pIter->pLeaf->p;
 int iRowidOffset = 0;

 if( n>pIter->iEndofDoclist ){
 n = pIter->iEndofDoclist;
 }

 ASSERT_SZLEAF_OK(pIter->pLeaf);
 while( 1 ){
 u64 iDelta = 0;

 if( eDetail==FTS5_DETAIL_NONE ){
 /* todo */
 if( i<n && a[i]==0 ){
 i++;
 if( i<n && a[i]==0 ) i++;
 }
 }else{
 int nPos;
 int bDummy;
 i += fts5GetPoslistSize(&a[i], &nPos, &bDummy);
 i += nPos;
 }
 if( i>=n ) break;
 i += fts5GetVarint(&a[i], &iDelta);
 pIter->iRowid += iDelta;

 /* If necessary, grow the pIter->aRowidOffset[] array. */
 if( iRowidOffset>=pIter->nRowidOffset ){
 int nNew = pIter->nRowidOffset + 8;
 int *aNew = (int*)sqlite3_realloc64(pIter->aRowidOffset,nNew*sizeof(int));
 if( aNew==0 ){
 p->rc = SQLITE_NOMEM;
 break;
 }
 pIter->aRowidOffset = aNew;
 pIter->nRowidOffset = nNew;
 }

 pIter->aRowidOffset[iRowidOffset++] = pIter->iLeafOffset;
 pIter->iLeafOffset = i;
 }
 pIter->iRowidOffset = iRowidOffset;
 fts5SegIterLoadNPos(p, pIter);
}

/*
**
*/
static void fts5SegIterReverseNewPage(Fts5Index *p, Fts5SegIter *pIter){
 assert( pIter->flags & FTS5_SEGITER_REVERSE );
 assert( pIter->flags & FTS5_SEGITER_ONETERM );

 fts5DataRelease(pIter->pLeaf);
 pIter->pLeaf = 0;
 while( p->rc==SQLITE_OK && pIter->iLeafPgno>pIter->iTermLeafPgno ){
 Fts5Data *pNew;
 pIter->iLeafPgno--;
 pNew = fts5DataRead(p, FTS5_SEGMENT_ROWID(
 pIter->pSeg->iSegid, pIter->iLeafPgno
 ));
 if( pNew ){
 /* iTermLeafOffset may be equal to szLeaf if the term is the last
 ** thing on the page - i.e. the first rowid is on the following page.
 ** In this case leave pIter->pLeaf==0, this iterator is at EOF. */
 if( pIter->iLeafPgno==pIter->iTermLeafPgno ){
 assert( pIter->pLeaf==0 );
 if( pIter->iTermLeafOffset<pNew->szLeaf ){
 pIter->pLeaf = pNew;
 pIter->iLeafOffset = pIter->iTermLeafOffset;
 }
 }else{
 int iRowidOff;
 iRowidOff = fts5LeafFirstRowidOff(pNew);
 if( iRowidOff ){
 if( iRowidOff>=pNew->szLeaf ){
 p->rc = FTS5_CORRUPT;
 }else{
 pIter->pLeaf = pNew;
 pIter->iLeafOffset = iRowidOff;
 }
 }
 }

 if( pIter->pLeaf ){
 u8 *a = &pIter->pLeaf->p[pIter->iLeafOffset];
 pIter->iLeafOffset += fts5GetVarint(a, (u64*)&pIter->iRowid);
 break;
 }else{
 fts5DataRelease(pNew);
 }
 }
 }

 if( pIter->pLeaf ){
 pIter->iEndofDoclist = pIter->pLeaf->nn+1;
 fts5SegIterReverseInitPage(p, pIter);
 }
}

/*
** Return true if the iterator passed as the second argument currently
** points to a delete marker. A delete marker is an entry with a 0 byte
** position-list.
*/
static int fts5MultiIterIsEmpty(Fts5Index *p, Fts5Iter *pIter){
 Fts5SegIter *pSeg = &pIter->aSeg[pIter->aFirst[1].iFirst];
 return (p->rc==SQLITE_OK && pSeg->pLeaf && pSeg->nPos==0);
}

/*
** Advance iterator pIter to the next entry.
**
** This version of fts5SegIterNext() is only used by reverse iterators.
*/
static void fts5SegIterNext_Reverse(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegIter *pIter, /* Iterator to advance */
 int *pbUnused /* Unused */
){
 assert( pIter->flags & FTS5_SEGITER_REVERSE );
 assert( pIter->pNextLeaf==0 );
 UNUSED_PARAM(pbUnused);

 if( pIter->iRowidOffset>0 ){
 u8 *a = pIter->pLeaf->p;
 int iOff;
 u64 iDelta;

 pIter->iRowidOffset--;
 pIter->iLeafOffset = pIter->aRowidOffset[pIter->iRowidOffset];
 fts5SegIterLoadNPos(p, pIter);
 iOff = pIter->iLeafOffset;
 if( p->pConfig->eDetail!=FTS5_DETAIL_NONE ){
 iOff += pIter->nPos;
 }
 fts5GetVarint(&a[iOff], &iDelta);
 pIter->iRowid -= iDelta;
 }else{
 fts5SegIterReverseNewPage(p, pIter);
 }
}

/*
** Advance iterator pIter to the next entry.
**
** This version of fts5SegIterNext() is only used if detail=none and the
** iterator is not a reverse direction iterator.
*/
static void fts5SegIterNext_None(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegIter *pIter, /* Iterator to advance */
 int *pbNewTerm /* OUT: Set for new term */
){
 int iOff;

 assert( p->rc==SQLITE_OK );
 assert( (pIter->flags & FTS5_SEGITER_REVERSE)==0 );
 assert( p->pConfig->eDetail==FTS5_DETAIL_NONE );

 ASSERT_SZLEAF_OK(pIter->pLeaf);
 iOff = pIter->iLeafOffset;

 /* Next entry is on the next page */
 while( pIter->pSeg && iOff>=pIter->pLeaf->szLeaf ){
 fts5SegIterNextPage(p, pIter);
 if( p->rc || pIter->pLeaf==0 ) return;
 pIter->iRowid = 0;
 iOff = 4;
 }

 if( iOff<pIter->iEndofDoclist ){
 /* Next entry is on the current page */
 u64 iDelta;
 iOff += sqlite3Fts5GetVarint(&pIter->pLeaf->p[iOff], (u64*)&iDelta);
 pIter->iLeafOffset = iOff;
 pIter->iRowid += iDelta;
 }else if( (pIter->flags & FTS5_SEGITER_ONETERM)==0 ){
 if( pIter->pSeg ){
 int nKeep = 0;
 if( iOff!=fts5LeafFirstTermOff(pIter->pLeaf) ){
 iOff += fts5GetVarint32(&pIter->pLeaf->p[iOff], nKeep);
 }
 pIter->iLeafOffset = iOff;
 fts5SegIterLoadTerm(p, pIter, nKeep);
 }else{
 const u8 *pList = 0;
 const char *zTerm = 0;
 int nTerm = 0;
 int nList;
 sqlite3Fts5HashScanNext(p->pHash);
 sqlite3Fts5HashScanEntry(p->pHash, &zTerm, &nTerm, &pList, &nList);
 if( pList==0 ) goto next_none_eof;
 pIter->pLeaf->p = (u8*)pList;
 pIter->pLeaf->nn = nList;
 pIter->pLeaf->szLeaf = nList;
 pIter->iEndofDoclist = nList;
 sqlite3Fts5BufferSet(&p->rc,&pIter->term, nTerm, (u8*)zTerm);
 pIter->iLeafOffset = fts5GetVarint(pList, (u64*)&pIter->iRowid);
 }

 if( pbNewTerm ) *pbNewTerm = 1;
 }else{
 goto next_none_eof;
 }

 fts5SegIterLoadNPos(p, pIter);

 return;
next_none_eof:
 fts5DataRelease(pIter->pLeaf);
 pIter->pLeaf = 0;
}

/*
** Advance iterator pIter to the next entry.
**
** If an error occurs, Fts5Index.rc is set to an appropriate error code. It
** is not considered an error if the iterator reaches EOF. If an error has
** already occurred when this function is called, it is a no-op.
*/
static void fts5SegIterNext(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegIter *pIter, /* Iterator to advance */
 int *pbNewTerm /* OUT: Set for new term */
){
 Fts5Data *pLeaf = pIter->pLeaf;
 int iOff;
 int bNewTerm = 0;
 int nKeep = 0;
 u8 *a;
 int n;

 assert( pbNewTerm==0 || *pbNewTerm==0 );
 assert( p->pConfig->eDetail!=FTS5_DETAIL_NONE );

 /* Search for the end of the position list within the current page. */
 a = pLeaf->p;
 n = pLeaf->szLeaf;

 ASSERT_SZLEAF_OK(pLeaf);
 iOff = pIter->iLeafOffset + pIter->nPos;

 if( iOff<n ){
 /* The next entry is on the current page. */
 assert_nc( iOff<=pIter->iEndofDoclist );
 if( iOff>=pIter->iEndofDoclist ){
 bNewTerm = 1;
 if( iOff!=fts5LeafFirstTermOff(pLeaf) ){
 iOff += fts5GetVarint32(&a[iOff], nKeep);
 }
 }else{
 u64 iDelta;
 iOff += sqlite3Fts5GetVarint(&a[iOff], &iDelta);
 pIter->iRowid += iDelta;
 assert_nc( iDelta>0 );
 }
 pIter->iLeafOffset = iOff;

 }else if( pIter->pSeg==0 ){
 const u8 *pList = 0;
 const char *zTerm = 0;
 int nTerm = 0;
 int nList = 0;
 assert( (pIter->flags & FTS5_SEGITER_ONETERM) || pbNewTerm );
 if( 0==(pIter->flags & FTS5_SEGITER_ONETERM) ){
 sqlite3Fts5HashScanNext(p->pHash);
 sqlite3Fts5HashScanEntry(p->pHash, &zTerm, &nTerm, &pList, &nList);
 }
 if( pList==0 ){
 fts5DataRelease(pIter->pLeaf);
 pIter->pLeaf = 0;
 }else{
 pIter->pLeaf->p = (u8*)pList;
 pIter->pLeaf->nn = nList;
 pIter->pLeaf->szLeaf = nList;
 pIter->iEndofDoclist = nList+1;
 sqlite3Fts5BufferSet(&p->rc, &pIter->term, nTerm, (u8*)zTerm);
 pIter->iLeafOffset = fts5GetVarint(pList, (u64*)&pIter->iRowid);
 *pbNewTerm = 1;
 }
 }else{
 iOff = 0;
 /* Next entry is not on the current page */
 while( iOff==0 ){
 fts5SegIterNextPage(p, pIter);
 pLeaf = pIter->pLeaf;
 if( pLeaf==0 ) break;
 ASSERT_SZLEAF_OK(pLeaf);
 if( (iOff = fts5LeafFirstRowidOff(pLeaf)) && iOff<pLeaf->szLeaf ){
 iOff += sqlite3Fts5GetVarint(&pLeaf->p[iOff], (u64*)&pIter->iRowid);
 pIter->iLeafOffset = iOff;

 if( pLeaf->nn>pLeaf->szLeaf ){
 pIter->iPgidxOff = pLeaf->szLeaf + fts5GetVarint32(
 &pLeaf->p[pLeaf->szLeaf], pIter->iEndofDoclist
 );
 }
 }
 else if( pLeaf->nn>pLeaf->szLeaf ){
 pIter->iPgidxOff = pLeaf->szLeaf + fts5GetVarint32(
 &pLeaf->p[pLeaf->szLeaf], iOff
 );
 pIter->iLeafOffset = iOff;
 pIter->iEndofDoclist = iOff;
 bNewTerm = 1;
 }
 assert_nc( iOff<pLeaf->szLeaf );
 if( iOff>pLeaf->szLeaf ){
 p->rc = FTS5_CORRUPT;
 return;
 }
 }
 }

 /* Check if the iterator is now at EOF. If so, return early. */
 if( pIter->pLeaf ){
 if( bNewTerm ){
 if( pIter->flags & FTS5_SEGITER_ONETERM ){
 fts5DataRelease(pIter->pLeaf);
 pIter->pLeaf = 0;
 }else{
 fts5SegIterLoadTerm(p, pIter, nKeep);
 fts5SegIterLoadNPos(p, pIter);
 if( pbNewTerm ) *pbNewTerm = 1;
 }
 }else{
 /* The following could be done by calling fts5SegIterLoadNPos(). But
 ** this block is particularly performance critical, so equivalent
 ** code is inlined. */
 int nSz;
 assert_nc( pIter->iLeafOffset<=pIter->pLeaf->nn );
 fts5FastGetVarint32(pIter->pLeaf->p, pIter->iLeafOffset, nSz);
 pIter->bDel = (nSz & 0x0001);
 pIter->nPos = nSz>>1;
 assert_nc( pIter->nPos>=0 );
 }
 }
}

#define SWAPVAL(T, a, b) { T tmp; tmp=a; a=b; b=tmp; }

#define fts5IndexSkipVarint(a, iOff) { \
 int iEnd = iOff+9; \
 while( (a[iOff++] & 0x80) && iOff<iEnd ); \
}

/*
** Iterator pIter currently points to the first rowid in a doclist. This
** function sets the iterator up so that iterates in reverse order through
** the doclist.
*/
static void fts5SegIterReverse(Fts5Index *p, Fts5SegIter *pIter){
 Fts5DlidxIter *pDlidx = pIter->pDlidx;
 Fts5Data *pLast = 0;
 int pgnoLast = 0;

 if( pDlidx && p->pConfig->iVersion==FTS5_CURRENT_VERSION ){
 int iSegid = pIter->pSeg->iSegid;
 pgnoLast = fts5DlidxIterPgno(pDlidx);
 pLast = fts5LeafRead(p, FTS5_SEGMENT_ROWID(iSegid, pgnoLast));
 }else{
 Fts5Data *pLeaf = pIter->pLeaf; /* Current leaf data */

 /* Currently, Fts5SegIter.iLeafOffset points to the first byte of
 ** position-list content for the current rowid. Back it up so that it
 ** points to the start of the position-list size field. */
 int iPoslist;
 if( pIter->iTermLeafPgno==pIter->iLeafPgno ){
 iPoslist = pIter->iTermLeafOffset;
 }else{
 iPoslist = 4;
 }
 fts5IndexSkipVarint(pLeaf->p, iPoslist);
 pIter->iLeafOffset = iPoslist;

 /* If this condition is true then the largest rowid for the current
 ** term may not be stored on the current page. So search forward to
 ** see where said rowid really is. */
 if( pIter->iEndofDoclist>=pLeaf->szLeaf ){
 int pgno;
 Fts5StructureSegment *pSeg = pIter->pSeg;

 /* The last rowid in the doclist may not be on the current page. Search
 ** forward to find the page containing the last rowid. */
 for(pgno=pIter->iLeafPgno+1; !p->rc && pgno<=pSeg->pgnoLast; pgno++){
 i64 iAbs = FTS5_SEGMENT_ROWID(pSeg->iSegid, pgno);
 Fts5Data *pNew = fts5LeafRead(p, iAbs);
 if( pNew ){
 int iRowid, bTermless;
 iRowid = fts5LeafFirstRowidOff(pNew);
 bTermless = fts5LeafIsTermless(pNew);
 if( iRowid ){
 SWAPVAL(Fts5Data*, pNew, pLast);
 pgnoLast = pgno;
 }
 fts5DataRelease(pNew);
 if( bTermless==0 ) break;
 }
 }
 }
 }

 /* If pLast is NULL at this point, then the last rowid for this doclist
 ** lies on the page currently indicated by the iterator. In this case
 ** pIter->iLeafOffset is already set to point to the position-list size
 ** field associated with the first relevant rowid on the page.
 **
 ** Or, if pLast is non-NULL, then it is the page that contains the last
 ** rowid. In this case configure the iterator so that it points to the
 ** first rowid on this page.
 */
 if( pLast ){
 int iOff;
 fts5DataRelease(pIter->pLeaf);
 pIter->pLeaf = pLast;
 pIter->iLeafPgno = pgnoLast;
 iOff = fts5LeafFirstRowidOff(pLast);
 if( iOff>pLast->szLeaf ){
 p->rc = FTS5_CORRUPT;
 return;
 }
 iOff += fts5GetVarint(&pLast->p[iOff], (u64*)&pIter->iRowid);
 pIter->iLeafOffset = iOff;

 if( fts5LeafIsTermless(pLast) ){
 pIter->iEndofDoclist = pLast->nn+1;
 }else{
 pIter->iEndofDoclist = fts5LeafFirstTermOff(pLast);
 }
 }

 fts5SegIterReverseInitPage(p, pIter);
}

/*
** Iterator pIter currently points to the first rowid of a doclist.
** There is a doclist-index associated with the final term on the current
** page. If the current term is the last term on the page, load the
** doclist-index from disk and initialize an iterator at (pIter->pDlidx).
*/
static void fts5SegIterLoadDlidx(Fts5Index *p, Fts5SegIter *pIter){
 int iSeg = pIter->pSeg->iSegid;
 int bRev = (pIter->flags & FTS5_SEGITER_REVERSE);
 Fts5Data *pLeaf = pIter->pLeaf; /* Current leaf data */

 assert( pIter->flags & FTS5_SEGITER_ONETERM );
 assert( pIter->pDlidx==0 );

 /* Check if the current doclist ends on this page. If it does, return
 ** early without loading the doclist-index (as it belongs to a different
 ** term. */
 if( pIter->iTermLeafPgno==pIter->iLeafPgno
 && pIter->iEndofDoclist<pLeaf->szLeaf
 ){
 return;
 }

 pIter->pDlidx = fts5DlidxIterInit(p, bRev, iSeg, pIter->iTermLeafPgno);
}

/*
** The iterator object passed as the second argument currently contains
** no valid values except for the Fts5SegIter.pLeaf member variable. This
** function searches the leaf page for a term matching (pTerm/nTerm).
**
** If the specified term is found on the page, then the iterator is left
** pointing to it. If argument bGe is zero and the term is not found,
** the iterator is left pointing at EOF.
**
** If bGe is non-zero and the specified term is not found, then the
** iterator is left pointing to the smallest term in the segment that
** is larger than the specified term, even if this term is not on the
** current page.
*/
static void fts5LeafSeek(
 Fts5Index *p, /* Leave any error code here */
 int bGe, /* True for a >= search */
 Fts5SegIter *pIter, /* Iterator to seek */
 const u8 *pTerm, int nTerm /* Term to search for */
){
 u32 iOff;
 const u8 *a = pIter->pLeaf->p;
 u32 n = (u32)pIter->pLeaf->nn;

 u32 nMatch = 0;
 u32 nKeep = 0;
 u32 nNew = 0;
 u32 iTermOff;
 u32 iPgidx; /* Current offset in pgidx */
 int bEndOfPage = 0;

 assert( p->rc==SQLITE_OK );

 iPgidx = (u32)pIter->pLeaf->szLeaf;
 iPgidx += fts5GetVarint32(&a[iPgidx], iTermOff);
 iOff = iTermOff;
 if( iOff>n ){
 p->rc = FTS5_CORRUPT;
 return;
 }

 while( 1 ){

 /* Figure out how many new bytes are in this term */
 fts5FastGetVarint32(a, iOff, nNew);
 if( nKeep<nMatch ){
 goto search_failed;
 }

 assert( nKeep>=nMatch );
 if( nKeep==nMatch ){
 u32 nCmp;
 u32 i;
 nCmp = (u32)MIN(nNew, nTerm-nMatch);
 for(i=0; i<nCmp; i++){
 if( a[iOff+i]!=pTerm[nMatch+i] ) break;
 }
 nMatch += i;

 if( (u32)nTerm==nMatch ){
 if( i==nNew ){
 goto search_success;
 }else{
 goto search_failed;
 }
 }else if( i<nNew && a[iOff+i]>pTerm[nMatch] ){
 goto search_failed;
 }
 }

 if( iPgidx>=n ){
 bEndOfPage = 1;
 break;
 }

 iPgidx += fts5GetVarint32(&a[iPgidx], nKeep);
 iTermOff += nKeep;
 iOff = iTermOff;

 if( iOff>=n ){
 p->rc = FTS5_CORRUPT;
 return;
 }

 /* Read the nKeep field of the next term. */
 fts5FastGetVarint32(a, iOff, nKeep);
 }

search_failed:
 if( bGe==0 ){
 fts5DataRelease(pIter->pLeaf);
 pIter->pLeaf = 0;
 return;
 }else if( bEndOfPage ){
 do {
 fts5SegIterNextPage(p, pIter);
 if( pIter->pLeaf==0 ) return;
 a = pIter->pLeaf->p;
 if( fts5LeafIsTermless(pIter->pLeaf)==0 ){
 iPgidx = (u32)pIter->pLeaf->szLeaf;
 iPgidx += fts5GetVarint32(&pIter->pLeaf->p[iPgidx], iOff);
 if( iOff<4 || (i64)iOff>=pIter->pLeaf->szLeaf ){
 p->rc = FTS5_CORRUPT;
 return;
 }else{
 nKeep = 0;
 iTermOff = iOff;
 n = (u32)pIter->pLeaf->nn;
 iOff += fts5GetVarint32(&a[iOff], nNew);
 break;
 }
 }
 }while( 1 );
 }

search_success:
 if( (i64)iOff+nNew>n || nNew<1 ){
 p->rc = FTS5_CORRUPT;
 return;
 }
 pIter->iLeafOffset = iOff + nNew;
 pIter->iTermLeafOffset = pIter->iLeafOffset;
 pIter->iTermLeafPgno = pIter->iLeafPgno;

 fts5BufferSet(&p->rc, &pIter->term, nKeep, pTerm);
 fts5BufferAppendBlob(&p->rc, &pIter->term, nNew, &a[iOff]);

 if( iPgidx>=n ){
 pIter->iEndofDoclist = pIter->pLeaf->nn+1;
 }else{
 int nExtra;
 iPgidx += fts5GetVarint32(&a[iPgidx], nExtra);
 pIter->iEndofDoclist = iTermOff + nExtra;
 }
 pIter->iPgidxOff = iPgidx;

 fts5SegIterLoadRowid(p, pIter);
 fts5SegIterLoadNPos(p, pIter);
}

static sqlite3_stmt *fts5IdxSelectStmt(Fts5Index *p){
 if( p->pIdxSelect==0 ){
 Fts5Config *pConfig = p->pConfig;
 fts5IndexPrepareStmt(p, &p->pIdxSelect, sqlite3_mprintf(
 "SELECT pgno FROM '%q'.'%q_idx' WHERE "
 "segid=? AND term<=? ORDER BY term DESC LIMIT 1",
 pConfig->zDb, pConfig->zName
 ));
 }
 return p->pIdxSelect;
}

/*
** Initialize the object pIter to point to term pTerm/nTerm within segment
** pSeg. If there is no such term in the index, the iterator is set to EOF.
**
** If an error occurs, Fts5Index.rc is set to an appropriate error code. If
** an error has already occurred when this function is called, it is a no-op.
*/
static void fts5SegIterSeekInit(
 Fts5Index *p, /* FTS5 backend */
 const u8 *pTerm, int nTerm, /* Term to seek to */
 int flags, /* Mask of FTS5INDEX_XXX flags */
 Fts5StructureSegment *pSeg, /* Description of segment */
 Fts5SegIter *pIter /* Object to populate */
){
 int iPg = 1;
 int bGe = (flags & FTS5INDEX_QUERY_SCAN);
 int bDlidx = 0; /* True if there is a doclist-index */
 sqlite3_stmt *pIdxSelect = 0;

 assert( bGe==0 || (flags & FTS5INDEX_QUERY_DESC)==0 );
 assert( pTerm && nTerm );
 memset(pIter, 0, sizeof(*pIter));
 pIter->pSeg = pSeg;

 /* This block sets stack variable iPg to the leaf page number that may
 ** contain term (pTerm/nTerm), if it is present in the segment. */
 pIdxSelect = fts5IdxSelectStmt(p);
 if( p->rc ) return;
 sqlite3_bind_int(pIdxSelect, 1, pSeg->iSegid);
 sqlite3_bind_blob(pIdxSelect, 2, pTerm, nTerm, SQLITE_STATIC);
 if( SQLITE_ROW==sqlite3_step(pIdxSelect) ){
 i64 val = sqlite3_column_int(pIdxSelect, 0);
 iPg = (int)(val>>1);
 bDlidx = (val & 0x0001);
 }
 p->rc = sqlite3_reset(pIdxSelect);
 sqlite3_bind_null(pIdxSelect, 2);

 if( iPg<pSeg->pgnoFirst ){
 iPg = pSeg->pgnoFirst;
 bDlidx = 0;
 }

 pIter->iLeafPgno = iPg - 1;
 fts5SegIterNextPage(p, pIter);

 if( pIter->pLeaf ){
 fts5LeafSeek(p, bGe, pIter, pTerm, nTerm);
 }

 if( p->rc==SQLITE_OK && (bGe==0 || (flags & FTS5INDEX_QUERY_SCANONETERM)) ){
 pIter->flags |= FTS5_SEGITER_ONETERM;
 if( pIter->pLeaf ){
 if( flags & FTS5INDEX_QUERY_DESC ){
 pIter->flags |= FTS5_SEGITER_REVERSE;
 }
 if( bDlidx ){
 fts5SegIterLoadDlidx(p, pIter);
 }
 if( flags & FTS5INDEX_QUERY_DESC ){
 fts5SegIterReverse(p, pIter);
 }
 }
 }

 fts5SegIterSetNext(p, pIter);
 if( 0==(flags & FTS5INDEX_QUERY_SCANONETERM) ){
 fts5SegIterAllocTombstone(p, pIter);
 }

 /* Either:
 **
 ** 1) an error has occurred, or
 ** 2) the iterator points to EOF, or
 ** 3) the iterator points to an entry with term (pTerm/nTerm), or
 ** 4) the FTS5INDEX_QUERY_SCAN flag was set and the iterator points
 ** to an entry with a term greater than or equal to (pTerm/nTerm).
 */
 assert_nc( p->rc!=SQLITE_OK /* 1 */
 || pIter->pLeaf==0 /* 2 */
 || fts5BufferCompareBlob(&pIter->term, pTerm, nTerm)==0 /* 3 */
 || (bGe && fts5BufferCompareBlob(&pIter->term, pTerm, nTerm)>0) /* 4 */
 );
}

/*
** SQL used by fts5SegIterNextInit() to find the page to open.
*/
static sqlite3_stmt *fts5IdxNextStmt(Fts5Index *p){
 if( p->pIdxNextSelect==0 ){
 Fts5Config *pConfig = p->pConfig;
 fts5IndexPrepareStmt(p, &p->pIdxNextSelect, sqlite3_mprintf(
 "SELECT pgno FROM '%q'.'%q_idx' WHERE "
 "segid=? AND term>? ORDER BY term ASC LIMIT 1",
 pConfig->zDb, pConfig->zName
 ));

 }
 return p->pIdxNextSelect;
}

/*
** This is similar to fts5SegIterSeekInit(), except that it initializes
** the segment iterator to point to the first term following the page
** with pToken/nToken on it.
*/
static void fts5SegIterNextInit(
 Fts5Index *p,
 const char *pTerm, int nTerm,
 Fts5StructureSegment *pSeg, /* Description of segment */
 Fts5SegIter *pIter /* Object to populate */
){
 int iPg = -1; /* Page of segment to open */
 int bDlidx = 0;
 sqlite3_stmt *pSel = 0; /* SELECT to find iPg */

 pSel = fts5IdxNextStmt(p);
 if( pSel ){
 assert( p->rc==SQLITE_OK );
 sqlite3_bind_int(pSel, 1, pSeg->iSegid);
 sqlite3_bind_blob(pSel, 2, pTerm, nTerm, SQLITE_STATIC);

 if( sqlite3_step(pSel)==SQLITE_ROW ){
 i64 val = sqlite3_column_int64(pSel, 0);
 iPg = (int)(val>>1);
 bDlidx = (val & 0x0001);
 }
 p->rc = sqlite3_reset(pSel);
 sqlite3_bind_null(pSel, 2);
 if( p->rc ) return;
 }

 memset(pIter, 0, sizeof(*pIter));
 pIter->pSeg = pSeg;
 pIter->flags |= FTS5_SEGITER_ONETERM;
 if( iPg>=0 ){
 pIter->iLeafPgno = iPg - 1;
 fts5SegIterNextPage(p, pIter);
 fts5SegIterSetNext(p, pIter);
 }
 if( pIter->pLeaf ){
 const u8 *a = pIter->pLeaf->p;
 int iTermOff = 0;

 pIter->iPgidxOff = pIter->pLeaf->szLeaf;
 pIter->iPgidxOff += fts5GetVarint32(&a[pIter->iPgidxOff], iTermOff);
 pIter->iLeafOffset = iTermOff;
 fts5SegIterLoadTerm(p, pIter, 0);
 fts5SegIterLoadNPos(p, pIter);
 if( bDlidx ) fts5SegIterLoadDlidx(p, pIter);

 assert( p->rc!=SQLITE_OK ||
 fts5BufferCompareBlob(&pIter->term, (const u8*)pTerm, nTerm)>0
 );
 }
}

/*
** Initialize the object pIter to point to term pTerm/nTerm within the
** in-memory hash table. If there is no such term in the hash-table, the
** iterator is set to EOF.
**
** If an error occurs, Fts5Index.rc is set to an appropriate error code. If
** an error has already occurred when this function is called, it is a no-op.
*/
static void fts5SegIterHashInit(
 Fts5Index *p, /* FTS5 backend */
 const u8 *pTerm, int nTerm, /* Term to seek to */
 int flags, /* Mask of FTS5INDEX_XXX flags */
 Fts5SegIter *pIter /* Object to populate */
){
 int nList = 0;
 const u8 *z = 0;
 int n = 0;
 Fts5Data *pLeaf = 0;

 assert( p->pHash );
 assert( p->rc==SQLITE_OK );

 if( pTerm==0 || (flags & FTS5INDEX_QUERY_SCAN) ){
 const u8 *pList = 0;

 p->rc = sqlite3Fts5HashScanInit(p->pHash, (const char*)pTerm, nTerm);
 sqlite3Fts5HashScanEntry(p->pHash, (const char**)&z, &n, &pList, &nList);
 if( pList ){
 pLeaf = fts5IdxMalloc(p, sizeof(Fts5Data));
 if( pLeaf ){
 pLeaf->p = (u8*)pList;
 }
 }

 /* The call to sqlite3Fts5HashScanInit() causes the hash table to
 ** fill the size field of all existing position lists. This means they
 ** can no longer be appended to. Since the only scenario in which they
 ** can be appended to is if the previous operation on this table was
 ** a DELETE, by clearing the Fts5Index.bDelete flag we can avoid this
 ** possibility altogether. */
 p->bDelete = 0;
 }else{
 p->rc = sqlite3Fts5HashQuery(p->pHash, sizeof(Fts5Data),
 (const char*)pTerm, nTerm, (void**)&pLeaf, &nList
 );
 if( pLeaf ){
 pLeaf->p = (u8*)&pLeaf[1];
 }
 z = pTerm;
 n = nTerm;
 pIter->flags |= FTS5_SEGITER_ONETERM;
 }

 if( pLeaf ){
 sqlite3Fts5BufferSet(&p->rc, &pIter->term, n, z);
 pLeaf->nn = pLeaf->szLeaf = nList;
 pIter->pLeaf = pLeaf;
 pIter->iLeafOffset = fts5GetVarint(pLeaf->p, (u64*)&pIter->iRowid);
 pIter->iEndofDoclist = pLeaf->nn;

 if( flags & FTS5INDEX_QUERY_DESC ){
 pIter->flags |= FTS5_SEGITER_REVERSE;
 fts5SegIterReverseInitPage(p, pIter);
 }else{
 fts5SegIterLoadNPos(p, pIter);
 }
 }

 fts5SegIterSetNext(p, pIter);
}

/*
** Array ap[] contains n elements. Release each of these elements using
** fts5DataRelease(). Then free the array itself using sqlite3_free().
*/
static void fts5IndexFreeArray(Fts5Data **ap, int n){
 if( ap ){
 int ii;
 for(ii=0; ii<n; ii++){
 fts5DataRelease(ap[ii]);
 }
 sqlite3_free(ap);
 }
}

/*
** Decrement the ref-count of the object passed as the only argument. If it
** reaches 0, free it and its contents.
*/
static void fts5TombstoneArrayDelete(Fts5TombstoneArray *p){
 if( p ){
 p->nRef--;
 if( p->nRef<=0 ){
 int ii;
 for(ii=0; ii<p->nTombstone; ii++){
 fts5DataRelease(p->apTombstone[ii]);
 }
 sqlite3_free(p);
 }
 }
}

/*
** Zero the iterator passed as the only argument.
*/
static void fts5SegIterClear(Fts5SegIter *pIter){
 fts5BufferFree(&pIter->term);
 fts5DataRelease(pIter->pLeaf);
 fts5DataRelease(pIter->pNextLeaf);
 fts5TombstoneArrayDelete(pIter->pTombArray);
 fts5DlidxIterFree(pIter->pDlidx);
 sqlite3_free(pIter->aRowidOffset);
 memset(pIter, 0, sizeof(Fts5SegIter));
}

#ifdef SQLITE_DEBUG

/*
** This function is used as part of the big assert() procedure implemented by
** fts5AssertMultiIterSetup(). It ensures that the result currently stored
** in *pRes is the correct result of comparing the current positions of the
** two iterators.
*/
static void fts5AssertComparisonResult(
 Fts5Iter *pIter,
 Fts5SegIter *p1,
 Fts5SegIter *p2,
 Fts5CResult *pRes
){
 int i1 = p1 - pIter->aSeg;
 int i2 = p2 - pIter->aSeg;

 if( p1->pLeaf || p2->pLeaf ){
 if( p1->pLeaf==0 ){
 assert( pRes->iFirst==i2 );
 }else if( p2->pLeaf==0 ){
 assert( pRes->iFirst==i1 );
 }else{
 int nMin = MIN(p1->term.n, p2->term.n);
 int res = fts5Memcmp(p1->term.p, p2->term.p, nMin);
 if( res==0 ) res = p1->term.n - p2->term.n;

 if( res==0 ){
 assert( pRes->bTermEq==1 );
 assert( p1->iRowid!=p2->iRowid );
 res = ((p1->iRowid > p2->iRowid)==pIter->bRev) ? -1 : 1;
 }else{
 assert( pRes->bTermEq==0 );
 }

 if( res<0 ){
 assert( pRes->iFirst==i1 );
 }else{
 assert( pRes->iFirst==i2 );
 }
 }
 }
}

/*
** This function is a no-op unless SQLITE_DEBUG is defined when this module
** is compiled. In that case, this function is essentially an assert()
** statement used to verify that the contents of the pIter->aFirst[] array
** are correct.
*/
static void fts5AssertMultiIterSetup(Fts5Index *p, Fts5Iter *pIter){
 if( p->rc==SQLITE_OK ){
 Fts5SegIter *pFirst = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
 int i;

 assert( (pFirst->pLeaf==0)==pIter->base.bEof );

 /* Check that pIter->iSwitchRowid is set correctly. */
 for(i=0; i<pIter->nSeg; i++){
 Fts5SegIter *p1 = &pIter->aSeg[i];
 assert( p1==pFirst
 || p1->pLeaf==0
 || fts5BufferCompare(&pFirst->term, &p1->term)
 || p1->iRowid==pIter->iSwitchRowid
 || (p1->iRowid<pIter->iSwitchRowid)==pIter->bRev
 );
 }

 for(i=0; i<pIter->nSeg; i+=2){
 Fts5SegIter *p1 = &pIter->aSeg[i];
 Fts5SegIter *p2 = &pIter->aSeg[i+1];
 Fts5CResult *pRes = &pIter->aFirst[(pIter->nSeg + i) / 2];
 fts5AssertComparisonResult(pIter, p1, p2, pRes);
 }

 for(i=1; i<(pIter->nSeg / 2); i+=2){
 Fts5SegIter *p1 = &pIter->aSeg[ pIter->aFirst[i*2].iFirst ];
 Fts5SegIter *p2 = &pIter->aSeg[ pIter->aFirst[i*2+1].iFirst ];
 Fts5CResult *pRes = &pIter->aFirst[i];
 fts5AssertComparisonResult(pIter, p1, p2, pRes);
 }
 }
}
#else
# define fts5AssertMultiIterSetup(x,y)
#endif

/*
** Do the comparison necessary to populate pIter->aFirst[iOut].
**
** If the returned value is non-zero, then it is the index of an entry
** in the pIter->aSeg[] array that is (a) not at EOF, and (b) pointing
** to a key that is a duplicate of another, higher priority,
** segment-iterator in the pSeg->aSeg[] array.
*/
static int fts5MultiIterDoCompare(Fts5Iter *pIter, int iOut){
 int i1; /* Index of left-hand Fts5SegIter */
 int i2; /* Index of right-hand Fts5SegIter */
 int iRes;
 Fts5SegIter *p1; /* Left-hand Fts5SegIter */
 Fts5SegIter *p2; /* Right-hand Fts5SegIter */
 Fts5CResult *pRes = &pIter->aFirst[iOut];

 assert( iOut<pIter->nSeg && iOut>0 );
 assert( pIter->bRev==0 || pIter->bRev==1 );

 if( iOut>=(pIter->nSeg/2) ){
 i1 = (iOut - pIter->nSeg/2) * 2;
 i2 = i1 + 1;
 }else{
 i1 = pIter->aFirst[iOut*2].iFirst;
 i2 = pIter->aFirst[iOut*2+1].iFirst;
 }
 p1 = &pIter->aSeg[i1];
 p2 = &pIter->aSeg[i2];

 pRes->bTermEq = 0;
 if( p1->pLeaf==0 ){ /* If p1 is at EOF */
 iRes = i2;
 }else if( p2->pLeaf==0 ){ /* If p2 is at EOF */
 iRes = i1;
 }else{
 int res = fts5BufferCompare(&p1->term, &p2->term);
 if( res==0 ){
 assert_nc( i2>i1 );
 assert_nc( i2!=0 );
 pRes->bTermEq = 1;
 if( p1->iRowid==p2->iRowid ){
 return i2;
 }
 res = ((p1->iRowid > p2->iRowid)==pIter->bRev) ? -1 : +1;
 }
 assert( res!=0 );
 if( res<0 ){
 iRes = i1;
 }else{
 iRes = i2;
 }
 }

 pRes->iFirst = (u16)iRes;
 return 0;
}

/*
** Move the seg-iter so that it points to the first rowid on page iLeafPgno.
** It is an error if leaf iLeafPgno does not exist. Unless the db is
** a 'secure-delete' db, if it contains no rowids then this is also an error.
*/
static void fts5SegIterGotoPage(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegIter *pIter, /* Iterator to advance */
 int iLeafPgno
){
 assert( iLeafPgno>pIter->iLeafPgno );

 if( iLeafPgno>pIter->pSeg->pgnoLast ){
 p->rc = FTS5_CORRUPT;
 }else{
 fts5DataRelease(pIter->pNextLeaf);
 pIter->pNextLeaf = 0;
 pIter->iLeafPgno = iLeafPgno-1;

 while( p->rc==SQLITE_OK ){
 int iOff;
 fts5SegIterNextPage(p, pIter);
 if( pIter->pLeaf==0 ) break;
 iOff = fts5LeafFirstRowidOff(pIter->pLeaf);
 if( iOff>0 ){
 u8 *a = pIter->pLeaf->p;
 int n = pIter->pLeaf->szLeaf;
 if( iOff<4 || iOff>=n ){
 p->rc = FTS5_CORRUPT;
 }else{
 iOff += fts5GetVarint(&a[iOff], (u64*)&pIter->iRowid);
 pIter->iLeafOffset = iOff;
 fts5SegIterLoadNPos(p, pIter);
 }
 break;
 }
 }
 }
}

/*
** Advance the iterator passed as the second argument until it is at or
** past rowid iFrom. Regardless of the value of iFrom, the iterator is
** always advanced at least once.
*/
static void fts5SegIterNextFrom(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegIter *pIter, /* Iterator to advance */
 i64 iMatch /* Advance iterator at least this far */
){
 int bRev = (pIter->flags & FTS5_SEGITER_REVERSE);
 Fts5DlidxIter *pDlidx = pIter->pDlidx;
 int iLeafPgno = pIter->iLeafPgno;
 int bMove = 1;

 assert( pIter->flags & FTS5_SEGITER_ONETERM );
 assert( pIter->pDlidx );
 assert( pIter->pLeaf );

 if( bRev==0 ){
 while( !fts5DlidxIterEof(p, pDlidx) && iMatch>fts5DlidxIterRowid(pDlidx) ){
 iLeafPgno = fts5DlidxIterPgno(pDlidx);
 fts5DlidxIterNext(p, pDlidx);
 }
 assert_nc( iLeafPgno>=pIter->iLeafPgno || p->rc );
 if( iLeafPgno>pIter->iLeafPgno ){
 fts5SegIterGotoPage(p, pIter, iLeafPgno);
 bMove = 0;
 }
 }else{
 assert( pIter->pNextLeaf==0 );
 assert( iMatch<pIter->iRowid );
 while( !fts5DlidxIterEof(p, pDlidx) && iMatch<fts5DlidxIterRowid(pDlidx) ){
 fts5DlidxIterPrev(p, pDlidx);
 }
 iLeafPgno = fts5DlidxIterPgno(pDlidx);

 assert( fts5DlidxIterEof(p, pDlidx) || iLeafPgno<=pIter->iLeafPgno );

 if( iLeafPgno<pIter->iLeafPgno ){
 pIter->iLeafPgno = iLeafPgno+1;
 fts5SegIterReverseNewPage(p, pIter);
 bMove = 0;
 }
 }

 do{
 if( bMove && p->rc==SQLITE_OK ) pIter->xNext(p, pIter, 0);
 if( pIter->pLeaf==0 ) break;
 if( bRev==0 && pIter->iRowid>=iMatch ) break;
 if( bRev!=0 && pIter->iRowid<=iMatch ) break;
 bMove = 1;
 }while( p->rc==SQLITE_OK );
}

/*
** Free the iterator object passed as the second argument.
*/
static void fts5MultiIterFree(Fts5Iter *pIter){
 if( pIter ){
 int i;
 for(i=0; i<pIter->nSeg; i++){
 fts5SegIterClear(&pIter->aSeg[i]);
 }
 fts5BufferFree(&pIter->poslist);
 sqlite3_free(pIter);
 }
}

static void fts5MultiIterAdvanced(
 Fts5Index *p, /* FTS5 backend to iterate within */
 Fts5Iter *pIter, /* Iterator to update aFirst[] array for */
 int iChanged, /* Index of sub-iterator just advanced */
 int iMinset /* Minimum entry in aFirst[] to set */
){
 int i;
 for(i=(pIter->nSeg+iChanged)/2; i>=iMinset && p->rc==SQLITE_OK; i=i/2){
 int iEq;
 if( (iEq = fts5MultiIterDoCompare(pIter, i)) ){
 Fts5SegIter *pSeg = &pIter->aSeg[iEq];
 assert( p->rc==SQLITE_OK );
 pSeg->xNext(p, pSeg, 0);
 i = pIter->nSeg + iEq;
 }
 }
}

/*
** Sub-iterator iChanged of iterator pIter has just been advanced. It still
** points to the same term though - just a different rowid. This function
** attempts to update the contents of the pIter->aFirst[] accordingly.
** If it does so successfully, 0 is returned. Otherwise 1.
**
** If non-zero is returned, the caller should call fts5MultiIterAdvanced()
** on the iterator instead. That function does the same as this one, except
** that it deals with more complicated cases as well.
*/
static int fts5MultiIterAdvanceRowid(
 Fts5Iter *pIter, /* Iterator to update aFirst[] array for */
 int iChanged, /* Index of sub-iterator just advanced */
 Fts5SegIter **ppFirst
){
 Fts5SegIter *pNew = &pIter->aSeg[iChanged];

 if( pNew->iRowid==pIter->iSwitchRowid
 || (pNew->iRowid<pIter->iSwitchRowid)==pIter->bRev
 ){
 int i;
 Fts5SegIter *pOther = &pIter->aSeg[iChanged ^ 0x0001];
 pIter->iSwitchRowid = pIter->bRev ? SMALLEST_INT64 : LARGEST_INT64;
 for(i=(pIter->nSeg+iChanged)/2; 1; i=i/2){
 Fts5CResult *pRes = &pIter->aFirst[i];

 assert( pNew->pLeaf );
 assert( pRes->bTermEq==0 || pOther->pLeaf );

 if( pRes->bTermEq ){
 if( pNew->iRowid==pOther->iRowid ){
 return 1;
 }else if( (pOther->iRowid>pNew->iRowid)==pIter->bRev ){
 pIter->iSwitchRowid = pOther->iRowid;
 pNew = pOther;
 }else if( (pOther->iRowid>pIter->iSwitchRowid)==pIter->bRev ){
 pIter->iSwitchRowid = pOther->iRowid;
 }
 }
 pRes->iFirst = (u16)(pNew - pIter->aSeg);
 if( i==1 ) break;

 pOther = &pIter->aSeg[ pIter->aFirst[i ^ 0x0001].iFirst ];
 }
 }

 *ppFirst = pNew;
 return 0;
}

/*
** Set the pIter->bEof variable based on the state of the sub-iterators.
*/
static void fts5MultiIterSetEof(Fts5Iter *pIter){
 Fts5SegIter *pSeg = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
 pIter->base.bEof = pSeg->pLeaf==0;
 pIter->iSwitchRowid = pSeg->iRowid;
}

/*
** The argument to this macro must be an Fts5Data structure containing a
** tombstone hash page. This macro returns the key-size of the hash-page.
*/
#define TOMBSTONE_KEYSIZE(pPg) (pPg->p[0]==4 ? 4 : 8)

#define TOMBSTONE_NSLOT(pPg) \
 ((pPg->nn > 16) ? ((pPg->nn-8) / TOMBSTONE_KEYSIZE(pPg)) : 1)

/*
** Query a single tombstone hash table for rowid iRowid. Return true if
** it is found or false otherwise. The tombstone hash table is one of
** nHashTable tables.
*/
static int fts5IndexTombstoneQuery(
 Fts5Data *pHash, /* Hash table page to query */
 int nHashTable, /* Number of pages attached to segment */
 u64 iRowid /* Rowid to query hash for */
){
 const int szKey = TOMBSTONE_KEYSIZE(pHash);
 const int nSlot = TOMBSTONE_NSLOT(pHash);
 int iSlot = (iRowid / nHashTable) % nSlot;
 int nCollide = nSlot;

 if( iRowid==0 ){
 return pHash->p[1];
 }else if( szKey==4 ){
 u32 *aSlot = (u32*)&pHash->p[8];
 while( aSlot[iSlot] ){
 if( fts5GetU32((u8*)&aSlot[iSlot])==iRowid ) return 1;
 if( nCollide--==0 ) break;
 iSlot = (iSlot+1)%nSlot;
 }
 }else{
 u64 *aSlot = (u64*)&pHash->p[8];
 while( aSlot[iSlot] ){
 if( fts5GetU64((u8*)&aSlot[iSlot])==iRowid ) return 1;
 if( nCollide--==0 ) break;
 iSlot = (iSlot+1)%nSlot;
 }
 }

 return 0;
}

/*
** Return true if the iterator passed as the only argument points
** to an segment entry for which there is a tombstone. Return false
** if there is no tombstone or if the iterator is already at EOF.
*/
static int fts5MultiIterIsDeleted(Fts5Iter *pIter){
 int iFirst = pIter->aFirst[1].iFirst;
 Fts5SegIter *pSeg = &pIter->aSeg[iFirst];
 Fts5TombstoneArray *pArray = pSeg->pTombArray;

 if( pSeg->pLeaf && pArray ){
 /* Figure out which page the rowid might be present on. */
 int iPg = ((u64)pSeg->iRowid) % pArray->nTombstone;
 assert( iPg>=0 );

 /* If tombstone hash page iPg has not yet been loaded from the
 ** database, load it now. */
 if( pArray->apTombstone[iPg]==0 ){
 pArray->apTombstone[iPg] = fts5DataRead(pIter->pIndex,
 FTS5_TOMBSTONE_ROWID(pSeg->pSeg->iSegid, iPg)
 );
 if( pArray->apTombstone[iPg]==0 ) return 0;
 }

 return fts5IndexTombstoneQuery(
 pArray->apTombstone[iPg],
 pArray->nTombstone,
 pSeg->iRowid
 );
 }

 return 0;
}

/*
** Move the iterator to the next entry.
**
** If an error occurs, an error code is left in Fts5Index.rc. It is not
** considered an error if the iterator reaches EOF, or if it is already at
** EOF when this function is called.
*/
static void fts5MultiIterNext(
 Fts5Index *p,
 Fts5Iter *pIter,
 int bFrom, /* True if argument iFrom is valid */
 i64 iFrom /* Advance at least as far as this */
){
 int bUseFrom = bFrom;
 assert( pIter->base.bEof==0 );
 while( p->rc==SQLITE_OK ){
 int iFirst = pIter->aFirst[1].iFirst;
 int bNewTerm = 0;
 Fts5SegIter *pSeg = &pIter->aSeg[iFirst];
 assert( p->rc==SQLITE_OK );
 if( bUseFrom && pSeg->pDlidx ){
 fts5SegIterNextFrom(p, pSeg, iFrom);
 }else{
 pSeg->xNext(p, pSeg, &bNewTerm);
 }

 if( pSeg->pLeaf==0 || bNewTerm
 || fts5MultiIterAdvanceRowid(pIter, iFirst, &pSeg)
 ){
 fts5MultiIterAdvanced(p, pIter, iFirst, 1);
 fts5MultiIterSetEof(pIter);
 pSeg = &pIter->aSeg[pIter->aFirst[1].iFirst];
 if( pSeg->pLeaf==0 ) return;
 }

 fts5AssertMultiIterSetup(p, pIter);
 assert( pSeg==&pIter->aSeg[pIter->aFirst[1].iFirst] && pSeg->pLeaf );
 if( (pIter->bSkipEmpty==0 || pSeg->nPos)
 && 0==fts5MultiIterIsDeleted(pIter)
 ){
 pIter->xSetOutputs(pIter, pSeg);
 return;
 }
 bUseFrom = 0;
 }
}

static void fts5MultiIterNext2(
 Fts5Index *p,
 Fts5Iter *pIter,
 int *pbNewTerm /* OUT: True if *might* be new term */
){
 assert( pIter->bSkipEmpty );
 if( p->rc==SQLITE_OK ){
 *pbNewTerm = 0;
 do{
 int iFirst = pIter->aFirst[1].iFirst;
 Fts5SegIter *pSeg = &pIter->aSeg[iFirst];
 int bNewTerm = 0;

 assert( p->rc==SQLITE_OK );
 pSeg->xNext(p, pSeg, &bNewTerm);
 if( pSeg->pLeaf==0 || bNewTerm
 || fts5MultiIterAdvanceRowid(pIter, iFirst, &pSeg)
 ){
 fts5MultiIterAdvanced(p, pIter, iFirst, 1);
 fts5MultiIterSetEof(pIter);
 *pbNewTerm = 1;
 }
 fts5AssertMultiIterSetup(p, pIter);

 }while( (fts5MultiIterIsEmpty(p, pIter) || fts5MultiIterIsDeleted(pIter))
 && (p->rc==SQLITE_OK)
 );
 }
}

static void fts5IterSetOutputs_Noop(Fts5Iter *pUnused1, Fts5SegIter *pUnused2){
 UNUSED_PARAM2(pUnused1, pUnused2);
}

static Fts5Iter *fts5MultiIterAlloc(
 Fts5Index *p, /* FTS5 backend to iterate within */
 int nSeg
){
 Fts5Iter *pNew;
 i64 nSlot; /* Power of two >= nSeg */

 for(nSlot=2; nSlot<nSeg; nSlot=nSlot*2);
 pNew = fts5IdxMalloc(p,
 sizeof(Fts5Iter) + /* pNew */
 sizeof(Fts5SegIter) * (nSlot-1) + /* pNew->aSeg[] */
 sizeof(Fts5CResult) * nSlot /* pNew->aFirst[] */
 );
 if( pNew ){
 pNew->nSeg = nSlot;
 pNew->aFirst = (Fts5CResult*)&pNew->aSeg[nSlot];
 pNew->pIndex = p;
 pNew->xSetOutputs = fts5IterSetOutputs_Noop;
 }
 return pNew;
}

static void fts5PoslistCallback(
 Fts5Index *pUnused,
 void *pContext,
 const u8 *pChunk, int nChunk
){
 UNUSED_PARAM(pUnused);
 assert_nc( nChunk>=0 );
 if( nChunk>0 ){
 fts5BufferSafeAppendBlob((Fts5Buffer*)pContext, pChunk, nChunk);
 }
}

typedef struct PoslistCallbackCtx PoslistCallbackCtx;
struct PoslistCallbackCtx {
 Fts5Buffer *pBuf; /* Append to this buffer */
 Fts5Colset *pColset; /* Restrict matches to this column */
 int eState; /* See above */
};

typedef struct PoslistOffsetsCtx PoslistOffsetsCtx;
struct PoslistOffsetsCtx {
 Fts5Buffer *pBuf; /* Append to this buffer */
 Fts5Colset *pColset; /* Restrict matches to this column */
 int iRead;
 int iWrite;
};

/*
** TODO: Make this more efficient!
*/
static int fts5IndexColsetTest(Fts5Colset *pColset, int iCol){
 int i;
 for(i=0; i<pColset->nCol; i++){
 if( pColset->aiCol[i]==iCol ) return 1;
 }
 return 0;
}

static void fts5PoslistOffsetsCallback(
 Fts5Index *pUnused,
 void *pContext,
 const u8 *pChunk, int nChunk
){
 PoslistOffsetsCtx *pCtx = (PoslistOffsetsCtx*)pContext;
 UNUSED_PARAM(pUnused);
 assert_nc( nChunk>=0 );
 if( nChunk>0 ){
 int i = 0;
 while( i<nChunk ){
 int iVal;
 i += fts5GetVarint32(&pChunk[i], iVal);
 iVal += pCtx->iRead - 2;
 pCtx->iRead = iVal;
 if( fts5IndexColsetTest(pCtx->pColset, iVal) ){
 fts5BufferSafeAppendVarint(pCtx->pBuf, iVal + 2 - pCtx->iWrite);
 pCtx->iWrite = iVal;
 }
 }
 }
}

static void fts5PoslistFilterCallback(
 Fts5Index *pUnused,
 void *pContext,
 const u8 *pChunk, int nChunk
){
 PoslistCallbackCtx *pCtx = (PoslistCallbackCtx*)pContext;
 UNUSED_PARAM(pUnused);
 assert_nc( nChunk>=0 );
 if( nChunk>0 ){
 /* Search through to find the first varint with value 1. This is the
 ** start of the next columns hits. */
 int i = 0;
 int iStart = 0;

 if( pCtx->eState==2 ){
 int iCol;
 fts5FastGetVarint32(pChunk, i, iCol);
 if( fts5IndexColsetTest(pCtx->pColset, iCol) ){
 pCtx->eState = 1;
 fts5BufferSafeAppendVarint(pCtx->pBuf, 1);
 }else{
 pCtx->eState = 0;
 }
 }

 do {
 while( i<nChunk && pChunk[i]!=0x01 ){
 while( pChunk[i] & 0x80 ) i++;
 i++;
 }
 if( pCtx->eState ){
 fts5BufferSafeAppendBlob(pCtx->pBuf, &pChunk[iStart], i-iStart);
 }
 if( i<nChunk ){
 int iCol;
 iStart = i;
 i++;
 if( i>=nChunk ){
 pCtx->eState = 2;
 }else{
 fts5FastGetVarint32(pChunk, i, iCol);
 pCtx->eState = fts5IndexColsetTest(pCtx->pColset, iCol);
 if( pCtx->eState ){
 fts5BufferSafeAppendBlob(pCtx->pBuf, &pChunk[iStart], i-iStart);
 iStart = i;
 }
 }
 }
 }while( i<nChunk );
 }
}

static void fts5ChunkIterate(
 Fts5Index *p, /* Index object */
 Fts5SegIter *pSeg, /* Poslist of this iterator */
 void *pCtx, /* Context pointer for xChunk callback */
 void (*xChunk)(Fts5Index*, void*, const u8*, int)
){
 int nRem = pSeg->nPos; /* Number of bytes still to come */
 Fts5Data *pData = 0;
 u8 *pChunk = &pSeg->pLeaf->p[pSeg->iLeafOffset];
 int nChunk = MIN(nRem, pSeg->pLeaf->szLeaf - pSeg->iLeafOffset);
 int pgno = pSeg->iLeafPgno;
 int pgnoSave = 0;

 /* This function does not work with detail=none databases. */
 assert( p->pConfig->eDetail!=FTS5_DETAIL_NONE );

 if( (pSeg->flags & FTS5_SEGITER_REVERSE)==0 ){
 pgnoSave = pgno+1;
 }

 while( 1 ){
 xChunk(p, pCtx, pChunk, nChunk);
 nRem -= nChunk;
 fts5DataRelease(pData);
 if( nRem<=0 ){
 break;
 }else if( pSeg->pSeg==0 ){
 p->rc = FTS5_CORRUPT;
 return;
 }else{
 pgno++;
 pData = fts5LeafRead(p, FTS5_SEGMENT_ROWID(pSeg->pSeg->iSegid, pgno));
 if( pData==0 ) break;
 pChunk = &pData->p[4];
 nChunk = MIN(nRem, pData->szLeaf - 4);
 if( pgno==pgnoSave ){
 assert( pSeg->pNextLeaf==0 );
 pSeg->pNextLeaf = pData;
 pData = 0;
 }
 }
 }
}

/*
** Iterator pIter currently points to a valid entry (not EOF). This
** function appends the position list data for the current entry to
** buffer pBuf. It does not make a copy of the position-list size
** field.
*/
static void fts5SegiterPoslist(
 Fts5Index *p,
 Fts5SegIter *pSeg,
 Fts5Colset *pColset,
 Fts5Buffer *pBuf
){
 assert( pBuf!=0 );
 assert( pSeg!=0 );
 if( 0==fts5BufferGrow(&p->rc, pBuf, pSeg->nPos+FTS5_DATA_ZERO_PADDING) ){
 assert( pBuf->p!=0 );
 assert( pBuf->nSpace >= pBuf->n+pSeg->nPos+FTS5_DATA_ZERO_PADDING );
 memset(&pBuf->p[pBuf->n+pSeg->nPos], 0, FTS5_DATA_ZERO_PADDING);
 if( pColset==0 ){
 fts5ChunkIterate(p, pSeg, (void*)pBuf, fts5PoslistCallback);
 }else{
 if( p->pConfig->eDetail==FTS5_DETAIL_FULL ){
 PoslistCallbackCtx sCtx;
 sCtx.pBuf = pBuf;
 sCtx.pColset = pColset;
 sCtx.eState = fts5IndexColsetTest(pColset, 0);
 assert( sCtx.eState==0 || sCtx.eState==1 );
 fts5ChunkIterate(p, pSeg, (void*)&sCtx, fts5PoslistFilterCallback);
 }else{
 PoslistOffsetsCtx sCtx;
 memset(&sCtx, 0, sizeof(sCtx));
 sCtx.pBuf = pBuf;
 sCtx.pColset = pColset;
 fts5ChunkIterate(p, pSeg, (void*)&sCtx, fts5PoslistOffsetsCallback);
 }
 }
 }
}

/*
** Parameter pPos points to a buffer containing a position list, size nPos.
** This function filters it according to pColset (which must be non-NULL)
** and sets pIter->base.pData/nData to point to the new position list.
** If memory is required for the new position list, use buffer pIter->poslist.
** Or, if the new position list is a contiguous subset of the input, set
** pIter->base.pData/nData to point directly to it.
**
** This function is a no-op if *pRc is other than SQLITE_OK when it is
** called. If an OOM error is encountered, *pRc is set to SQLITE_NOMEM
** before returning.
*/
static void fts5IndexExtractColset(
 int *pRc,
 Fts5Colset *pColset, /* Colset to filter on */
 const u8 *pPos, int nPos, /* Position list */
 Fts5Iter *pIter
){
 if( *pRc==SQLITE_OK ){
 const u8 *p = pPos;
 const u8 *aCopy = p;
 const u8 *pEnd = &p[nPos]; /* One byte past end of position list */
 int i = 0;
 int iCurrent = 0;

 if( pColset->nCol>1 && sqlite3Fts5BufferSize(pRc, &pIter->poslist, nPos) ){
 return;
 }

 while( 1 ){
 while( pColset->aiCol[i]<iCurrent ){
 i++;
 if( i==pColset->nCol ){
 pIter->base.pData = pIter->poslist.p;
 pIter->base.nData = pIter->poslist.n;
 return;
 }
 }

 /* Advance pointer p until it points to pEnd or an 0x01 byte that is
 ** not part of a varint */
 while( p<pEnd && *p!=0x01 ){
 while( *p++ & 0x80 );
 }

 if( pColset->aiCol[i]==iCurrent ){
 if( pColset->nCol==1 ){
 pIter->base.pData = aCopy;
 pIter->base.nData = p-aCopy;
 return;
 }
 fts5BufferSafeAppendBlob(&pIter->poslist, aCopy, p-aCopy);
 }
 if( p>=pEnd ){
 pIter->base.pData = pIter->poslist.p;
 pIter->base.nData = pIter->poslist.n;
 return;
 }
 aCopy = p++;
 iCurrent = *p++;
 if( iCurrent & 0x80 ){
 p--;
 p += fts5GetVarint32(p, iCurrent);
 }
 }
 }

}

/*
** xSetOutputs callback used by detail=none tables.
*/
static void fts5IterSetOutputs_None(Fts5Iter *pIter, Fts5SegIter *pSeg){
 assert( pIter->pIndex->pConfig->eDetail==FTS5_DETAIL_NONE );
 pIter->base.iRowid = pSeg->iRowid;
 pIter->base.nData = pSeg->nPos;
}

/*
** xSetOutputs callback used by detail=full and detail=col tables when no
** column filters are specified.
*/
static void fts5IterSetOutputs_Nocolset(Fts5Iter *pIter, Fts5SegIter *pSeg){
 pIter->base.iRowid = pSeg->iRowid;
 pIter->base.nData = pSeg->nPos;

 assert( pIter->pIndex->pConfig->eDetail!=FTS5_DETAIL_NONE );
 assert( pIter->pColset==0 );

 if( pSeg->iLeafOffset+pSeg->nPos<=pSeg->pLeaf->szLeaf ){
 /* All data is stored on the current page. Populate the output
 ** variables to point into the body of the page object. */
 pIter->base.pData = &pSeg->pLeaf->p[pSeg->iLeafOffset];
 }else{
 /* The data is distributed over two or more pages. Copy it into the
 ** Fts5Iter.poslist buffer and then set the output pointer to point
 ** to this buffer. */
 fts5BufferZero(&pIter->poslist);
 fts5SegiterPoslist(pIter->pIndex, pSeg, 0, &pIter->poslist);
 pIter->base.pData = pIter->poslist.p;
 }
}

/*
** xSetOutputs callback used when the Fts5Colset object has nCol==0 (match
** against no columns at all).
*/
static void fts5IterSetOutputs_ZeroColset(Fts5Iter *pIter, Fts5SegIter *pSeg){
 UNUSED_PARAM(pSeg);
 pIter->base.nData = 0;
}

/*
** xSetOutputs callback used by detail=col when there is a column filter
** and there are 100 or more columns. Also called as a fallback from
** fts5IterSetOutputs_Col100 if the column-list spans more than one page.
*/
static void fts5IterSetOutputs_Col(Fts5Iter *pIter, Fts5SegIter *pSeg){
 fts5BufferZero(&pIter->poslist);
 fts5SegiterPoslist(pIter->pIndex, pSeg, pIter->pColset, &pIter->poslist);
 pIter->base.iRowid = pSeg->iRowid;
 pIter->base.pData = pIter->poslist.p;
 pIter->base.nData = pIter->poslist.n;
}

/*
** xSetOutputs callback used when:
**
** * detail=col,
** * there is a column filter, and
** * the table contains 100 or fewer columns.
**
** The last point is to ensure all column numbers are stored as
** single-byte varints.
*/
static void fts5IterSetOutputs_Col100(Fts5Iter *pIter, Fts5SegIter *pSeg){

 assert( pIter->pIndex->pConfig->eDetail==FTS5_DETAIL_COLUMNS );
 assert( pIter->pColset );

 if( pSeg->iLeafOffset+pSeg->nPos>pSeg->pLeaf->szLeaf ){
 fts5IterSetOutputs_Col(pIter, pSeg);
 }else{
 u8 *a = (u8*)&pSeg->pLeaf->p[pSeg->iLeafOffset];
 u8 *pEnd = (u8*)&a[pSeg->nPos];
 int iPrev = 0;
 int *aiCol = pIter->pColset->aiCol;
 int *aiColEnd = &aiCol[pIter->pColset->nCol];

 u8 *aOut = pIter->poslist.p;
 int iPrevOut = 0;

 pIter->base.iRowid = pSeg->iRowid;

 while( a<pEnd ){
 iPrev += (int)a++[0] - 2;
 while( *aiCol<iPrev ){
 aiCol++;
 if( aiCol==aiColEnd ) goto setoutputs_col_out;
 }
 if( *aiCol==iPrev ){
 *aOut++ = (u8)((iPrev - iPrevOut) + 2);
 iPrevOut = iPrev;
 }
 }

setoutputs_col_out:
 pIter->base.pData = pIter->poslist.p;
 pIter->base.nData = aOut - pIter->poslist.p;
 }
}

/*
** xSetOutputs callback used by detail=full when there is a column filter.
*/
static void fts5IterSetOutputs_Full(Fts5Iter *pIter, Fts5SegIter *pSeg){
 Fts5Colset *pColset = pIter->pColset;
 pIter->base.iRowid = pSeg->iRowid;

 assert( pIter->pIndex->pConfig->eDetail==FTS5_DETAIL_FULL );
 assert( pColset );

 if( pSeg->iLeafOffset+pSeg->nPos<=pSeg->pLeaf->szLeaf ){
 /* All data is stored on the current page. Populate the output
 ** variables to point into the body of the page object. */
 const u8 *a = &pSeg->pLeaf->p[pSeg->iLeafOffset];
 int *pRc = &pIter->pIndex->rc;
 fts5BufferZero(&pIter->poslist);
 fts5IndexExtractColset(pRc, pColset, a, pSeg->nPos, pIter);
 }else{
 /* The data is distributed over two or more pages. Copy it into the
 ** Fts5Iter.poslist buffer and then set the output pointer to point
 ** to this buffer. */
 fts5BufferZero(&pIter->poslist);
 fts5SegiterPoslist(pIter->pIndex, pSeg, pColset, &pIter->poslist);
 pIter->base.pData = pIter->poslist.p;
 pIter->base.nData = pIter->poslist.n;
 }
}

static void fts5IterSetOutputCb(int *pRc, Fts5Iter *pIter){
 assert( pIter!=0 || (*pRc)!=SQLITE_OK );
 if( *pRc==SQLITE_OK ){
 Fts5Config *pConfig = pIter->pIndex->pConfig;
 if( pConfig->eDetail==FTS5_DETAIL_NONE ){
 pIter->xSetOutputs = fts5IterSetOutputs_None;
 }

 else if( pIter->pColset==0 ){
 pIter->xSetOutputs = fts5IterSetOutputs_Nocolset;
 }

 else if( pIter->pColset->nCol==0 ){
 pIter->xSetOutputs = fts5IterSetOutputs_ZeroColset;
 }

 else if( pConfig->eDetail==FTS5_DETAIL_FULL ){
 pIter->xSetOutputs = fts5IterSetOutputs_Full;
 }

 else{
 assert( pConfig->eDetail==FTS5_DETAIL_COLUMNS );
 if( pConfig->nCol<=100 ){
 pIter->xSetOutputs = fts5IterSetOutputs_Col100;
 sqlite3Fts5BufferSize(pRc, &pIter->poslist, pConfig->nCol);
 }else{
 pIter->xSetOutputs = fts5IterSetOutputs_Col;
 }
 }
 }
}

/*
** All the component segment-iterators of pIter have been set up. This
** functions finishes setup for iterator pIter itself.
*/
static void fts5MultiIterFinishSetup(Fts5Index *p, Fts5Iter *pIter){
 int iIter;
 for(iIter=pIter->nSeg-1; iIter>0; iIter--){
 int iEq;
 if( (iEq = fts5MultiIterDoCompare(pIter, iIter)) ){
 Fts5SegIter *pSeg = &pIter->aSeg[iEq];
 if( p->rc==SQLITE_OK ) pSeg->xNext(p, pSeg, 0);
 fts5MultiIterAdvanced(p, pIter, iEq, iIter);
 }
 }
 fts5MultiIterSetEof(pIter);
 fts5AssertMultiIterSetup(p, pIter);

 if( (pIter->bSkipEmpty && fts5MultiIterIsEmpty(p, pIter))
 || fts5MultiIterIsDeleted(pIter)
 ){
 fts5MultiIterNext(p, pIter, 0, 0);
 }else if( pIter->base.bEof==0 ){
 Fts5SegIter *pSeg = &pIter->aSeg[pIter->aFirst[1].iFirst];
 pIter->xSetOutputs(pIter, pSeg);
 }
}

/*
** Allocate a new Fts5Iter object.
**
** The new object will be used to iterate through data in structure pStruct.
** If iLevel is -ve, then all data in all segments is merged. Or, if iLevel
** is zero or greater, data from the first nSegment segments on level iLevel
** is merged.
**
** The iterator initially points to the first term/rowid entry in the
** iterated data.
*/
static void fts5MultiIterNew(
 Fts5Index *p, /* FTS5 backend to iterate within */
 Fts5Structure *pStruct, /* Structure of specific index */
 int flags, /* FTS5INDEX_QUERY_XXX flags */
 Fts5Colset *pColset, /* Colset to filter on (or NULL) */
 const u8 *pTerm, int nTerm, /* Term to seek to (or NULL/0) */
 int iLevel, /* Level to iterate (-1 for all) */
 int nSegment, /* Number of segments to merge (iLevel>=0) */
 Fts5Iter **ppOut /* New object */
){
 int nSeg = 0; /* Number of segment-iters in use */
 int iIter = 0; /* */
 int iSeg; /* Used to iterate through segments */
 Fts5StructureLevel *pLvl;
 Fts5Iter *pNew;

 assert( (pTerm==0 && nTerm==0) || iLevel<0 );

 /* Allocate space for the new multi-seg-iterator. */
 if( p->rc==SQLITE_OK ){
 if( iLevel<0 ){
 assert( pStruct->nSegment==fts5StructureCountSegments(pStruct) );
 nSeg = pStruct->nSegment;
 nSeg += (p->pHash && 0==(flags & FTS5INDEX_QUERY_SKIPHASH));
 }else{
 nSeg = MIN(pStruct->aLevel[iLevel].nSeg, nSegment);
 }
 }
 *ppOut = pNew = fts5MultiIterAlloc(p, nSeg);
 if( pNew==0 ){
 assert( p->rc!=SQLITE_OK );
 goto fts5MultiIterNew_post_check;
 }
 pNew->bRev = (0!=(flags & FTS5INDEX_QUERY_DESC));
 pNew->bSkipEmpty = (0!=(flags & FTS5INDEX_QUERY_SKIPEMPTY));
 pNew->pColset = pColset;
 if( (flags & FTS5INDEX_QUERY_NOOUTPUT)==0 ){
 fts5IterSetOutputCb(&p->rc, pNew);
 }

 /* Initialize each of the component segment iterators. */
 if( p->rc==SQLITE_OK ){
 if( iLevel<0 ){
 Fts5StructureLevel *pEnd = &pStruct->aLevel[pStruct->nLevel];
 if( p->pHash && 0==(flags & FTS5INDEX_QUERY_SKIPHASH) ){
 /* Add a segment iterator for the current contents of the hash table. */
 Fts5SegIter *pIter = &pNew->aSeg[iIter++];
 fts5SegIterHashInit(p, pTerm, nTerm, flags, pIter);
 }
 for(pLvl=&pStruct->aLevel[0]; pLvl<pEnd; pLvl++){
 for(iSeg=pLvl->nSeg-1; iSeg>=0; iSeg--){
 Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
 Fts5SegIter *pIter = &pNew->aSeg[iIter++];
 if( pTerm==0 ){
 fts5SegIterInit(p, pSeg, pIter);
 }else{
 fts5SegIterSeekInit(p, pTerm, nTerm, flags, pSeg, pIter);
 }
 }
 }
 }else{
 pLvl = &pStruct->aLevel[iLevel];
 for(iSeg=nSeg-1; iSeg>=0; iSeg--){
 fts5SegIterInit(p, &pLvl->aSeg[iSeg], &pNew->aSeg[iIter++]);
 }
 }
 assert( iIter==nSeg );
 }

 /* If the above was successful, each component iterator now points
 ** to the first entry in its segment. In this case initialize the
 ** aFirst[] array. Or, if an error has occurred, free the iterator
 ** object and set the output variable to NULL. */
 if( p->rc==SQLITE_OK ){
 fts5MultiIterFinishSetup(p, pNew);
 }else{
 fts5MultiIterFree(pNew);
 *ppOut = 0;
 }

fts5MultiIterNew_post_check:
 assert( (*ppOut)!=0 || p->rc!=SQLITE_OK );
 return;
}

/*
** Create an Fts5Iter that iterates through the doclist provided
** as the second argument.
*/
static void fts5MultiIterNew2(
 Fts5Index *p, /* FTS5 backend to iterate within */
 Fts5Data *pData, /* Doclist to iterate through */
 int bDesc, /* True for descending rowid order */
 Fts5Iter **ppOut /* New object */
){
 Fts5Iter *pNew;
 pNew = fts5MultiIterAlloc(p, 2);
 if( pNew ){
 Fts5SegIter *pIter = &pNew->aSeg[1];
 pIter->flags = FTS5_SEGITER_ONETERM;
 if( pData->szLeaf>0 ){
 pIter->pLeaf = pData;
 pIter->iLeafOffset = fts5GetVarint(pData->p, (u64*)&pIter->iRowid);
 pIter->iEndofDoclist = pData->nn;
 pNew->aFirst[1].iFirst = 1;
 if( bDesc ){
 pNew->bRev = 1;
 pIter->flags |= FTS5_SEGITER_REVERSE;
 fts5SegIterReverseInitPage(p, pIter);
 }else{
 fts5SegIterLoadNPos(p, pIter);
 }
 pData = 0;
 }else{
 pNew->base.bEof = 1;
 }
 fts5SegIterSetNext(p, pIter);

 *ppOut = pNew;
 }

 fts5DataRelease(pData);
}

/*
** Return true if the iterator is at EOF or if an error has occurred.
** False otherwise.
*/
static int fts5MultiIterEof(Fts5Index *p, Fts5Iter *pIter){
 assert( pIter!=0 || p->rc!=SQLITE_OK );
 assert( p->rc!=SQLITE_OK
 || (pIter->aSeg[ pIter->aFirst[1].iFirst ].pLeaf==0)==pIter->base.bEof
 );
 return (p->rc || pIter->base.bEof);
}

/*
** Return the rowid of the entry that the iterator currently points
** to. If the iterator points to EOF when this function is called the
** results are undefined.
*/
static i64 fts5MultiIterRowid(Fts5Iter *pIter){
 assert( pIter->aSeg[ pIter->aFirst[1].iFirst ].pLeaf );
 return pIter->aSeg[ pIter->aFirst[1].iFirst ].iRowid;
}

/*
** Move the iterator to the next entry at or following iMatch.
*/
static void fts5MultiIterNextFrom(
 Fts5Index *p,
 Fts5Iter *pIter,
 i64 iMatch
){
 while( 1 ){
 i64 iRowid;
 fts5MultiIterNext(p, pIter, 1, iMatch);
 if( fts5MultiIterEof(p, pIter) ) break;
 iRowid = fts5MultiIterRowid(pIter);
 if( pIter->bRev==0 && iRowid>=iMatch ) break;
 if( pIter->bRev!=0 && iRowid<=iMatch ) break;
 }
}

/*
** Return a pointer to a buffer containing the term associated with the
** entry that the iterator currently points to.
*/
static const u8 *fts5MultiIterTerm(Fts5Iter *pIter, int *pn){
 Fts5SegIter *p = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
 *pn = p->term.n;
 return p->term.p;
}

/*
** Allocate a new segment-id for the structure pStruct. The new segment
** id must be between 1 and 65335 inclusive, and must not be used by
** any currently existing segment. If a free segment id cannot be found,
** SQLITE_FULL is returned.
**
** If an error has already occurred, this function is a no-op. 0 is
** returned in this case.
*/
static int fts5AllocateSegid(Fts5Index *p, Fts5Structure *pStruct){
 int iSegid = 0;

 if( p->rc==SQLITE_OK ){
 if( pStruct->nSegment>=FTS5_MAX_SEGMENT ){
 p->rc = SQLITE_FULL;
 }else{
 /* FTS5_MAX_SEGMENT is currently defined as 2000. So the following
 ** array is 63 elements, or 252 bytes, in size. */
 u32 aUsed[(FTS5_MAX_SEGMENT+31) / 32];
 int iLvl, iSeg;
 int i;
 u32 mask;
 memset(aUsed, 0, sizeof(aUsed));
 for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
 for(iSeg=0; iSeg<pStruct->aLevel[iLvl].nSeg; iSeg++){
 int iId = pStruct->aLevel[iLvl].aSeg[iSeg].iSegid;
 if( iId<=FTS5_MAX_SEGMENT && iId>0 ){
 aUsed[(iId-1) / 32] |= (u32)1 << ((iId-1) % 32);
 }
 }
 }

 for(i=0; aUsed[i]==0xFFFFFFFF; i++);
 mask = aUsed[i];
 for(iSegid=0; mask & ((u32)1 << iSegid); iSegid++);
 iSegid += 1 + i*32;

#ifdef SQLITE_DEBUG
 for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
 for(iSeg=0; iSeg<pStruct->aLevel[iLvl].nSeg; iSeg++){
 assert_nc( iSegid!=pStruct->aLevel[iLvl].aSeg[iSeg].iSegid );
 }
 }
 assert_nc( iSegid>0 && iSegid<=FTS5_MAX_SEGMENT );

 {
 sqlite3_stmt *pIdxSelect = fts5IdxSelectStmt(p);
 if( p->rc==SQLITE_OK ){
 u8 aBlob[2] = {0xff, 0xff};
 sqlite3_bind_int(pIdxSelect, 1, iSegid);
 sqlite3_bind_blob(pIdxSelect, 2, aBlob, 2, SQLITE_STATIC);
 assert_nc( sqlite3_step(pIdxSelect)!=SQLITE_ROW );
 p->rc = sqlite3_reset(pIdxSelect);
 sqlite3_bind_null(pIdxSelect, 2);
 }
 }
#endif
 }
 }

 return iSegid;
}

/*
** Discard all data currently cached in the hash-tables.
*/
static void fts5IndexDiscardData(Fts5Index *p){
 assert( p->pHash || p->nPendingData==0 );
 if( p->pHash ){
 sqlite3Fts5HashClear(p->pHash);
 p->nPendingData = 0;
 p->nPendingRow = 0;
 p->flushRc = SQLITE_OK;
 }
 p->nContentlessDelete = 0;
}

/*
** Return the size of the prefix, in bytes, that buffer
** (pNew/<length-unknown>) shares with buffer (pOld/nOld).
**
** Buffer (pNew/<length-unknown>) is guaranteed to be greater
** than buffer (pOld/nOld).
*/
static int fts5PrefixCompress(int nOld, const u8 *pOld, const u8 *pNew){
 int i;
 for(i=0; i<nOld; i++){
 if( pOld[i]!=pNew[i] ) break;
 }
 return i;
}

static void fts5WriteDlidxClear(
 Fts5Index *p,
 Fts5SegWriter *pWriter,
 int bFlush /* If true, write dlidx to disk */
){
 int i;
 assert( bFlush==0 || (pWriter->nDlidx>0 && pWriter->aDlidx[0].buf.n>0) );
 for(i=0; i<pWriter->nDlidx; i++){
 Fts5DlidxWriter *pDlidx = &pWriter->aDlidx[i];
 if( pDlidx->buf.n==0 ) break;
 if( bFlush ){
 assert( pDlidx->pgno!=0 );
 fts5DataWrite(p,
 FTS5_DLIDX_ROWID(pWriter->iSegid, i, pDlidx->pgno),
 pDlidx->buf.p, pDlidx->buf.n
 );
 }
 sqlite3Fts5BufferZero(&pDlidx->buf);
 pDlidx->bPrevValid = 0;
 }
}

/*
** Grow the pWriter->aDlidx[] array to at least nLvl elements in size.
** Any new array elements are zeroed before returning.
*/
static int fts5WriteDlidxGrow(
 Fts5Index *p,
 Fts5SegWriter *pWriter,
 int nLvl
){
 if( p->rc==SQLITE_OK && nLvl>=pWriter->nDlidx ){
 Fts5DlidxWriter *aDlidx = (Fts5DlidxWriter*)sqlite3_realloc64(
 pWriter->aDlidx, sizeof(Fts5DlidxWriter) * nLvl
 );
 if( aDlidx==0 ){
 p->rc = SQLITE_NOMEM;
 }else{
 size_t nByte = sizeof(Fts5DlidxWriter) * (nLvl - pWriter->nDlidx);
 memset(&aDlidx[pWriter->nDlidx], 0, nByte);
 pWriter->aDlidx = aDlidx;
 pWriter->nDlidx = nLvl;
 }
 }
 return p->rc;
}

/*
** If the current doclist-index accumulating in pWriter->aDlidx[] is large
** enough, flush it to disk and return 1. Otherwise discard it and return
** zero.
*/
static int fts5WriteFlushDlidx(Fts5Index *p, Fts5SegWriter *pWriter){
 int bFlag = 0;

 /* If there were FTS5_MIN_DLIDX_SIZE or more empty leaf pages written
 ** to the database, also write the doclist-index to disk. */
 if( pWriter->aDlidx[0].buf.n>0 && pWriter->nEmpty>=FTS5_MIN_DLIDX_SIZE ){
 bFlag = 1;
 }
 fts5WriteDlidxClear(p, pWriter, bFlag);
 pWriter->nEmpty = 0;
 return bFlag;
}

/*
** This function is called whenever processing of the doclist for the
** last term on leaf page (pWriter->iBtPage) is completed.
**
** The doclist-index for that term is currently stored in-memory within the
** Fts5SegWriter.aDlidx[] array. If it is large enough, this function
** writes it out to disk. Or, if it is too small to bother with, discards
** it.
**
** Fts5SegWriter.btterm currently contains the first term on page iBtPage.
*/
static void fts5WriteFlushBtree(Fts5Index *p, Fts5SegWriter *pWriter){
 int bFlag;

 assert( pWriter->iBtPage || pWriter->nEmpty==0 );
 if( pWriter->iBtPage==0 ) return;
 bFlag = fts5WriteFlushDlidx(p, pWriter);

 if( p->rc==SQLITE_OK ){
 const char *z = (pWriter->btterm.n>0?(const char*)pWriter->btterm.p:"");
 /* The following was already done in fts5WriteInit(): */
 /* sqlite3_bind_int(p->pIdxWriter, 1, pWriter->iSegid); */
 sqlite3_bind_blob(p->pIdxWriter, 2, z, pWriter->btterm.n, SQLITE_STATIC);
 sqlite3_bind_int64(p->pIdxWriter, 3, bFlag + ((i64)pWriter->iBtPage<<1));
 sqlite3_step(p->pIdxWriter);
 p->rc = sqlite3_reset(p->pIdxWriter);
 sqlite3_bind_null(p->pIdxWriter, 2);
 }
 pWriter->iBtPage = 0;
}

/*
** This is called once for each leaf page except the first that contains
** at least one term. Argument (nTerm/pTerm) is the split-key - a term that
** is larger than all terms written to earlier leaves, and equal to or
** smaller than the first term on the new leaf.
**
** If an error occurs, an error code is left in Fts5Index.rc. If an error
** has already occurred when this function is called, it is a no-op.
*/
static void fts5WriteBtreeTerm(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegWriter *pWriter, /* Writer object */
 int nTerm, const u8 *pTerm /* First term on new page */
){
 fts5WriteFlushBtree(p, pWriter);
 if( p->rc==SQLITE_OK ){
 fts5BufferSet(&p->rc, &pWriter->btterm, nTerm, pTerm);
 pWriter->iBtPage = pWriter->writer.pgno;
 }
}

/*
** This function is called when flushing a leaf page that contains no
** terms at all to disk.
*/
static void fts5WriteBtreeNoTerm(
 Fts5Index *p, /* FTS5 backend object */
 Fts5SegWriter *pWriter /* Writer object */
){
 /* If there were no rowids on the leaf page either and the doclist-index
 ** has already been started, append an 0x00 byte to it. */
 if( pWriter->bFirstRowidInPage && pWriter->aDlidx[0].buf.n>0 ){
 Fts5DlidxWriter *pDlidx = &pWriter->aDlidx[0];
 assert( pDlidx->bPrevValid );
 sqlite3Fts5BufferAppendVarint(&p->rc, &pDlidx->buf, 0);
 }

 /* Increment the "number of sequential leaves without a term" counter. */
 pWriter->nEmpty++;
}

static i64 fts5DlidxExtractFirstRowid(Fts5Buffer *pBuf){
 i64 iRowid;
 int iOff;

 iOff = 1 + fts5GetVarint(&pBuf->p[1], (u64*)&iRowid);
 fts5GetVarint(&pBuf->p[iOff], (u64*)&iRowid);
 return iRowid;
}

/*
** Rowid iRowid has just been appended to the current leaf page. It is the
** first on the page. This function appends an appropriate entry to the current
** doclist-index.
*/
static void fts5WriteDlidxAppend(
 Fts5Index *p,
 Fts5SegWriter *pWriter,
 i64 iRowid
){
 int i;
 int bDone = 0;

 for(i=0; p->rc==SQLITE_OK && bDone==0; i++){
 i64 iVal;
 Fts5DlidxWriter *pDlidx = &pWriter->aDlidx[i];

 if( pDlidx->buf.n>=p->pConfig->pgsz ){
 /* The current doclist-index page is full. Write it to disk and push
 ** a copy of iRowid (which will become the first rowid on the next
 ** doclist-index leaf page) up into the next level of the b-tree
 ** hierarchy. If the node being flushed is currently the root node,
 ** also push its first rowid upwards. */
 pDlidx->buf.p[0] = 0x01; /* Not the root node */
 fts5DataWrite(p,
 FTS5_DLIDX_ROWID(pWriter->iSegid, i, pDlidx->pgno),
 pDlidx->buf.p, pDlidx->buf.n
 );
 fts5WriteDlidxGrow(p, pWriter, i+2);
 pDlidx = &pWriter->aDlidx[i];
 if( p->rc==SQLITE_OK && pDlidx[1].buf.n==0 ){
 i64 iFirst = fts5DlidxExtractFirstRowid(&pDlidx->buf);

 /* This was the root node. Push its first rowid up to the new root. */
 pDlidx[1].pgno = pDlidx->pgno;
 sqlite3Fts5BufferAppendVarint(&p->rc, &pDlidx[1].buf, 0);
 sqlite3Fts5BufferAppendVarint(&p->rc, &pDlidx[1].buf, pDlidx->pgno);
 sqlite3Fts5BufferAppendVarint(&p->rc, &pDlidx[1].buf, iFirst);
 pDlidx[1].bPrevValid = 1;
 pDlidx[1].iPrev = iFirst;
 }

 sqlite3Fts5BufferZero(&pDlidx->buf);
 pDlidx->bPrevValid = 0;
 pDlidx->pgno++;
 }else{
 bDone = 1;
 }

 if( pDlidx->bPrevValid ){
 iVal = (u64)iRowid - (u64)pDlidx->iPrev;
 }else{
 i64 iPgno = (i==0 ? pWriter->writer.pgno : pDlidx[-1].pgno);
 assert( pDlidx->buf.n==0 );
 sqlite3Fts5BufferAppendVarint(&p->rc, &pDlidx->buf, !bDone);
 sqlite3Fts5BufferAppendVarint(&p->rc, &pDlidx->buf, iPgno);
 iVal = iRowid;
 }

 sqlite3Fts5BufferAppendVarint(&p->rc, &pDlidx->buf, iVal);
 pDlidx->bPrevValid = 1;
 pDlidx->iPrev = iRowid;
 }
}

static void fts5WriteFlushLeaf(Fts5Index *p, Fts5SegWriter *pWriter){
 static const u8 zero[] = { 0x00, 0x00, 0x00, 0x00 };
 Fts5PageWriter *pPage = &pWriter->writer;
 i64 iRowid;

 assert( (pPage->pgidx.n==0)==(pWriter->bFirstTermInPage) );

 /* Set the szLeaf header field. */
 assert( 0==fts5GetU16(&pPage->buf.p[2]) );
 fts5PutU16(&pPage->buf.p[2], (u16)pPage->buf.n);

 if( pWriter->bFirstTermInPage ){
 /* No term was written to this page. */
 assert( pPage->pgidx.n==0 );
 fts5WriteBtreeNoTerm(p, pWriter);
 }else{
 /* Append the pgidx to the page buffer. Set the szLeaf header field. */
 fts5BufferAppendBlob(&p->rc, &pPage->buf, pPage->pgidx.n, pPage->pgidx.p);
 }

 /* Write the page out to disk */
 iRowid = FTS5_SEGMENT_ROWID(pWriter->iSegid, pPage->pgno);
 fts5DataWrite(p, iRowid, pPage->buf.p, pPage->buf.n);

 /* Initialize the next page. */
 fts5BufferZero(&pPage->buf);
 fts5BufferZero(&pPage->pgidx);
 fts5BufferAppendBlob(&p->rc, &pPage->buf, 4, zero);
 pPage->iPrevPgidx = 0;
 pPage->pgno++;

 /* Increase the leaves written counter */
 pWriter->nLeafWritten++;

 /* The new leaf holds no terms or rowids */
 pWriter->bFirstTermInPage = 1;
 pWriter->bFirstRowidInPage = 1;
}

/*
** Append term pTerm/nTerm to the segment being written by the writer passed
** as the second argument.
**
** If an error occurs, set the Fts5Index.rc error code. If an error has
** already occurred, this function is a no-op.
*/
static void fts5WriteAppendTerm(
 Fts5Index *p,
 Fts5SegWriter *pWriter,
 int nTerm, const u8 *pTerm
){
 int nPrefix; /* Bytes of prefix compression for term */
 Fts5PageWriter *pPage = &pWriter->writer;
 Fts5Buffer *pPgidx = &pWriter->writer.pgidx;
 int nMin = MIN(pPage->term.n, nTerm);

 assert( p->rc==SQLITE_OK );
 assert( pPage->buf.n>=4 );
 assert( pPage->buf.n>4 || pWriter->bFirstTermInPage );

 /* If the current leaf page is full, flush it to disk. */
 if( (pPage->buf.n + pPgidx->n + nTerm + 2)>=p->pConfig->pgsz ){
 if( pPage->buf.n>4 ){
 fts5WriteFlushLeaf(p, pWriter);
 if( p->rc!=SQLITE_OK ) return;
 }
 fts5BufferGrow(&p->rc, &pPage->buf, nTerm+FTS5_DATA_PADDING);
 }

 /* TODO1: Updating pgidx here. */
 pPgidx->n += sqlite3Fts5PutVarint(
 &pPgidx->p[pPgidx->n], pPage->buf.n - pPage->iPrevPgidx
 );
 pPage->iPrevPgidx = pPage->buf.n;
#if 0
 fts5PutU16(&pPgidx->p[pPgidx->n], pPage->buf.n);
 pPgidx->n += 2;
#endif

 if( pWriter->bFirstTermInPage ){
 nPrefix = 0;
 if( pPage->pgno!=1 ){
 /* This is the first term on a leaf that is not the leftmost leaf in
 ** the segment b-tree. In this case it is necessary to add a term to
 ** the b-tree hierarchy that is (a) larger than the largest term
 ** already written to the segment and (b) smaller than or equal to
 ** this term. In other words, a prefix of (pTerm/nTerm) that is one
 ** byte longer than the longest prefix (pTerm/nTerm) shares with the
 ** previous term.
 **
 ** Usually, the previous term is available in pPage->term. The exception
 ** is if this is the first term written in an incremental-merge step.
 ** In this case the previous term is not available, so just write a
 ** copy of (pTerm/nTerm) into the parent node. This is slightly
 ** inefficient, but still correct. */
 int n = nTerm;
 if( pPage->term.n ){
 n = 1 + fts5PrefixCompress(nMin, pPage->term.p, pTerm);
 }
 fts5WriteBtreeTerm(p, pWriter, n, pTerm);
 if( p->rc!=SQLITE_OK ) return;
 pPage = &pWriter->writer;
 }
 }else{
 nPrefix = fts5PrefixCompress(nMin, pPage->term.p, pTerm);
 fts5BufferAppendVarint(&p->rc, &pPage->buf, nPrefix);
 }

 /* Append the number of bytes of new data, then the term data itself
 ** to the page. */
 fts5BufferAppendVarint(&p->rc, &pPage->buf, nTerm - nPrefix);
 fts5BufferAppendBlob(&p->rc, &pPage->buf, nTerm - nPrefix, &pTerm[nPrefix]);

 /* Update the Fts5PageWriter.term field. */
 fts5BufferSet(&p->rc, &pPage->term, nTerm, pTerm);
 pWriter->bFirstTermInPage = 0;

 pWriter->bFirstRowidInPage = 0;
 pWriter->bFirstRowidInDoclist = 1;

 assert( p->rc || (pWriter->nDlidx>0 && pWriter->aDlidx[0].buf.n==0) );
 pWriter->aDlidx[0].pgno = pPage->pgno;
}

/*
** Append a rowid and position-list size field to the writers output.
*/
static void fts5WriteAppendRowid(
 Fts5Index *p,
 Fts5SegWriter *pWriter,
 i64 iRowid
){
 if( p->rc==SQLITE_OK ){
 Fts5PageWriter *pPage = &pWriter->writer;

 if( (pPage->buf.n + pPage->pgidx.n)>=p->pConfig->pgsz ){
 fts5WriteFlushLeaf(p, pWriter);
 }

 /* If this is to be the first rowid written to the page, set the
 ** rowid-pointer in the page-header. Also append a value to the dlidx
 ** buffer, in case a doclist-index is required. */
 if( pWriter->bFirstRowidInPage ){
 fts5PutU16(pPage->buf.p, (u16)pPage->buf.n);
 fts5WriteDlidxAppend(p, pWriter, iRowid);
 }

 /* Write the rowid. */
 if( pWriter->bFirstRowidInDoclist || pWriter->bFirstRowidInPage ){
 fts5BufferAppendVarint(&p->rc, &pPage->buf, iRowid);
 }else{
 assert_nc( p->rc || iRowid>pWriter->iPrevRowid );
 fts5BufferAppendVarint(&p->rc, &pPage->buf,
 (u64)iRowid - (u64)pWriter->iPrevRowid
 );
 }
 pWriter->iPrevRowid = iRowid;
 pWriter->bFirstRowidInDoclist = 0;
 pWriter->bFirstRowidInPage = 0;
 }
}

static void fts5WriteAppendPoslistData(
 Fts5Index *p,
 Fts5SegWriter *pWriter,
 const u8 *aData,
 int nData
){
 Fts5PageWriter *pPage = &pWriter->writer;
 const u8 *a = aData;
 int n = nData;

 assert( p->pConfig->pgsz>0 || p->rc!=SQLITE_OK );
 while( p->rc==SQLITE_OK
 && (pPage->buf.n + pPage->pgidx.n + n)>=p->pConfig->pgsz
 ){
 int nReq = p->pConfig->pgsz - pPage->buf.n - pPage->pgidx.n;
 int nCopy = 0;
 while( nCopy<nReq ){
 i64 dummy;
 nCopy += fts5GetVarint(&a[nCopy], (u64*)&dummy);
 }
 fts5BufferAppendBlob(&p->rc, &pPage->buf, nCopy, a);
 a += nCopy;
 n -= nCopy;
 fts5WriteFlushLeaf(p, pWriter);
 }
 if( n>0 ){
 fts5BufferAppendBlob(&p->rc, &pPage->buf, n, a);
 }
}

/*
** Flush any data cached by the writer object to the database. Free any
** allocations associated with the writer.
*/
static void fts5WriteFinish(
 Fts5Index *p,
 Fts5SegWriter *pWriter, /* Writer object */
 int *pnLeaf /* OUT: Number of leaf pages in b-tree */
){
 int i;
 Fts5PageWriter *pLeaf = &pWriter->writer;
 if( p->rc==SQLITE_OK ){
 assert( pLeaf->pgno>=1 );
 if( pLeaf->buf.n>4 ){
 fts5WriteFlushLeaf(p, pWriter);
 }
 *pnLeaf = pLeaf->pgno-1;
 if( pLeaf->pgno>1 ){
 fts5WriteFlushBtree(p, pWriter);
 }
 }
 fts5BufferFree(&pLeaf->term);
 fts5BufferFree(&pLeaf->buf);
 fts5BufferFree(&pLeaf->pgidx);
 fts5BufferFree(&pWriter->btterm);

 for(i=0; i<pWriter->nDlidx; i++){
 sqlite3Fts5BufferFree(&pWriter->aDlidx[i].buf);
 }
 sqlite3_free(pWriter->aDlidx);
}

static void fts5WriteInit(
 Fts5Index *p,
 Fts5SegWriter *pWriter,
 int iSegid
){
 const int nBuffer = p->pConfig->pgsz + FTS5_DATA_PADDING;

 memset(pWriter, 0, sizeof(Fts5SegWriter));
 pWriter->iSegid = iSegid;

 fts5WriteDlidxGrow(p, pWriter, 1);
 pWriter->writer.pgno = 1;
 pWriter->bFirstTermInPage = 1;
 pWriter->iBtPage = 1;

 assert( pWriter->writer.buf.n==0 );
 assert( pWriter->writer.pgidx.n==0 );

 /* Grow the two buffers to pgsz + padding bytes in size. */
 sqlite3Fts5BufferSize(&p->rc, &pWriter->writer.pgidx, nBuffer);
 sqlite3Fts5BufferSize(&p->rc, &pWriter->writer.buf, nBuffer);

 if( p->pIdxWriter==0 ){
 Fts5Config *pConfig = p->pConfig;
 fts5IndexPrepareStmt(p, &p->pIdxWriter, sqlite3_mprintf(
 "INSERT INTO '%q'.'%q_idx'(segid,term,pgno) VALUES(?,?,?)",
 pConfig->zDb, pConfig->zName
 ));
 }

 if( p->rc==SQLITE_OK ){
 /* Initialize the 4-byte leaf-page header to 0x00. */
 memset(pWriter->writer.buf.p, 0, 4);
 pWriter->writer.buf.n = 4;

 /* Bind the current output segment id to the index-writer. This is an
 ** optimization over binding the same value over and over as rows are
 ** inserted into %_idx by the current writer. */
 sqlite3_bind_int(p->pIdxWriter, 1, pWriter->iSegid);
 }
}

/*
** Iterator pIter was used to iterate through the input segments of on an
** incremental merge operation. This function is called if the incremental
** merge step has finished but the input has not been completely exhausted.
*/
static void fts5TrimSegments(Fts5Index *p, Fts5Iter *pIter){
 int i;
 Fts5Buffer buf;
 memset(&buf, 0, sizeof(Fts5Buffer));
 for(i=0; i<pIter->nSeg && p->rc==SQLITE_OK; i++){
 Fts5SegIter *pSeg = &pIter->aSeg[i];
 if( pSeg->pSeg==0 ){
 /* no-op */
 }else if( pSeg->pLeaf==0 ){
 /* All keys from this input segment have been transfered to the output.
 ** Set both the first and last page-numbers to 0 to indicate that the
 ** segment is now empty. */
 pSeg->pSeg->pgnoLast = 0;
 pSeg->pSeg->pgnoFirst = 0;
 }else{
 int iOff = pSeg->iTermLeafOffset; /* Offset on new first leaf page */
 i64 iLeafRowid;
 Fts5Data *pData;
 int iId = pSeg->pSeg->iSegid;
 u8 aHdr[4] = {0x00, 0x00, 0x00, 0x00};

 iLeafRowid = FTS5_SEGMENT_ROWID(iId, pSeg->iTermLeafPgno);
 pData = fts5LeafRead(p, iLeafRowid);
 if( pData ){
 if( iOff>pData->szLeaf ){
 /* This can occur if the pages that the segments occupy overlap - if
 ** a single page has been assigned to more than one segment. In
 ** this case a prior iteration of this loop may have corrupted the
 ** segment currently being trimmed. */
 p->rc = FTS5_CORRUPT;
 }else{
 fts5BufferZero(&buf);
 fts5BufferGrow(&p->rc, &buf, pData->nn);
 fts5BufferAppendBlob(&p->rc, &buf, sizeof(aHdr), aHdr);
 fts5BufferAppendVarint(&p->rc, &buf, pSeg->term.n);
 fts5BufferAppendBlob(&p->rc, &buf, pSeg->term.n, pSeg->term.p);
 fts5BufferAppendBlob(&p->rc, &buf,pData->szLeaf-iOff,&pData->p[iOff]);
 if( p->rc==SQLITE_OK ){
 /* Set the szLeaf field */
 fts5PutU16(&buf.p[2], (u16)buf.n);
 }

 /* Set up the new page-index array */
 fts5BufferAppendVarint(&p->rc, &buf, 4);
 if( pSeg->iLeafPgno==pSeg->iTermLeafPgno
 && pSeg->iEndofDoclist<pData->szLeaf
 && pSeg->iPgidxOff<=pData->nn
 ){
 int nDiff = pData->szLeaf - pSeg->iEndofDoclist;
 fts5BufferAppendVarint(&p->rc, &buf, buf.n - 1 - nDiff - 4);
 fts5BufferAppendBlob(&p->rc, &buf,
 pData->nn - pSeg->iPgidxOff, &pData->p[pSeg->iPgidxOff]
 );
 }

 pSeg->pSeg->pgnoFirst = pSeg->iTermLeafPgno;
 fts5DataDelete(p, FTS5_SEGMENT_ROWID(iId, 1), iLeafRowid);
 fts5DataWrite(p, iLeafRowid, buf.p, buf.n);
 }
 fts5DataRelease(pData);
 }
 }
 }
 fts5BufferFree(&buf);
}

static void fts5MergeChunkCallback(
 Fts5Index *p,
 void *pCtx,
 const u8 *pChunk, int nChunk
){
 Fts5SegWriter *pWriter = (Fts5SegWriter*)pCtx;
 fts5WriteAppendPoslistData(p, pWriter, pChunk, nChunk);
}

/*
**
*/
static void fts5IndexMergeLevel(
 Fts5Index *p, /* FTS5 backend object */
 Fts5Structure **ppStruct, /* IN/OUT: Stucture of index */
 int iLvl, /* Level to read input from */
 int *pnRem /* Write up to this many output leaves */
){
 Fts5Structure *pStruct = *ppStruct;
 Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
 Fts5StructureLevel *pLvlOut;
 Fts5Iter *pIter = 0; /* Iterator to read input data */
 int nRem = pnRem ? *pnRem : 0; /* Output leaf pages left to write */
 int nInput; /* Number of input segments */
 Fts5SegWriter writer; /* Writer object */
 Fts5StructureSegment *pSeg; /* Output segment */
 Fts5Buffer term;
 int bOldest; /* True if the output segment is the oldest */
 int eDetail = p->pConfig->eDetail;
 const int flags = FTS5INDEX_QUERY_NOOUTPUT;
 int bTermWritten = 0; /* True if current term already output */

 assert( iLvl<pStruct->nLevel );
 assert( pLvl->nMerge<=pLvl->nSeg );

 memset(&writer, 0, sizeof(Fts5SegWriter));
 memset(&term, 0, sizeof(Fts5Buffer));
 if( pLvl->nMerge ){
 pLvlOut = &pStruct->aLevel[iLvl+1];
 assert( pLvlOut->nSeg>0 );
 nInput = pLvl->nMerge;
 pSeg = &pLvlOut->aSeg[pLvlOut->nSeg-1];

 fts5WriteInit(p, &writer, pSeg->iSegid);
 writer.writer.pgno = pSeg->pgnoLast+1;
 writer.iBtPage = 0;
 }else{
 int iSegid = fts5AllocateSegid(p, pStruct);

 /* Extend the Fts5Structure object as required to ensure the output
 ** segment exists. */
 if( iLvl==pStruct->nLevel-1 ){
 fts5StructureAddLevel(&p->rc, ppStruct);
 pStruct = *ppStruct;
 }
 fts5StructureExtendLevel(&p->rc, pStruct, iLvl+1, 1, 0);
 if( p->rc ) return;
 pLvl = &pStruct->aLevel[iLvl];
 pLvlOut = &pStruct->aLevel[iLvl+1];

 fts5WriteInit(p, &writer, iSegid);

 /* Add the new segment to the output level */
 pSeg = &pLvlOut->aSeg[pLvlOut->nSeg];
 pLvlOut->nSeg++;
 pSeg->pgnoFirst = 1;
 pSeg->iSegid = iSegid;
 pStruct->nSegment++;

 /* Read input from all segments in the input level */
 nInput = pLvl->nSeg;

 /* Set the range of origins that will go into the output segment. */
 if( pStruct->nOriginCntr>0 ){
 pSeg->iOrigin1 = pLvl->aSeg[0].iOrigin1;
 pSeg->iOrigin2 = pLvl->aSeg[pLvl->nSeg-1].iOrigin2;
 }
 }
 bOldest = (pLvlOut->nSeg==1 && pStruct->nLevel==iLvl+2);

 assert( iLvl>=0 );
 for(fts5MultiIterNew(p, pStruct, flags, 0, 0, 0, iLvl, nInput, &pIter);
 fts5MultiIterEof(p, pIter)==0;
 fts5MultiIterNext(p, pIter, 0, 0)
 ){
 Fts5SegIter *pSegIter = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
 int nPos; /* position-list size field value */
 int nTerm;
 const u8 *pTerm;

 pTerm = fts5MultiIterTerm(pIter, &nTerm);
 if( nTerm!=term.n || fts5Memcmp(pTerm, term.p, nTerm) ){
 if( pnRem && writer.nLeafWritten>nRem ){
 break;
 }
 fts5BufferSet(&p->rc, &term, nTerm, pTerm);
 bTermWritten =0;
 }

 /* Check for key annihilation. */
 if( pSegIter->nPos==0 && (bOldest || pSegIter->bDel==0) ) continue;

 if( p->rc==SQLITE_OK && bTermWritten==0 ){
 /* This is a new term. Append a term to the output segment. */
 fts5WriteAppendTerm(p, &writer, nTerm, pTerm);
 bTermWritten = 1;
 }

 /* Append the rowid to the output */
 /* WRITEPOSLISTSIZE */
 fts5WriteAppendRowid(p, &writer, fts5MultiIterRowid(pIter));

 if( eDetail==FTS5_DETAIL_NONE ){
 if( pSegIter->bDel ){
 fts5BufferAppendVarint(&p->rc, &writer.writer.buf, 0);
 if( pSegIter->nPos>0 ){
 fts5BufferAppendVarint(&p->rc, &writer.writer.buf, 0);
 }
 }
 }else{
 /* Append the position-list data to the output */
 nPos = pSegIter->nPos*2 + pSegIter->bDel;
 fts5BufferAppendVarint(&p->rc, &writer.writer.buf, nPos);
 fts5ChunkIterate(p, pSegIter, (void*)&writer, fts5MergeChunkCallback);
 }
 }

 /* Flush the last leaf page to disk. Set the output segment b-tree height
 ** and last leaf page number at the same time. */
 fts5WriteFinish(p, &writer, &pSeg->pgnoLast);

 assert( pIter!=0 || p->rc!=SQLITE_OK );
 if( fts5MultiIterEof(p, pIter) ){
 int i;

 /* Remove the redundant segments from the %_data table */
 assert( pSeg->nEntry==0 );
 for(i=0; i<nInput; i++){
 Fts5StructureSegment *pOld = &pLvl->aSeg[i];
 pSeg->nEntry += (pOld->nEntry - pOld->nEntryTombstone);
 fts5DataRemoveSegment(p, pOld);
 }

 /* Remove the redundant segments from the input level */
 if( pLvl->nSeg!=nInput ){
 int nMove = (pLvl->nSeg - nInput) * sizeof(Fts5StructureSegment);
 memmove(pLvl->aSeg, &pLvl->aSeg[nInput], nMove);
 }
 pStruct->nSegment -= nInput;
 pLvl->nSeg -= nInput;
 pLvl->nMerge = 0;
 if( pSeg->pgnoLast==0 ){
 pLvlOut->nSeg--;
 pStruct->nSegment--;
 }
 }else{
 assert( pSeg->pgnoLast>0 );
 fts5TrimSegments(p, pIter);
 pLvl->nMerge = nInput;
 }

 fts5MultiIterFree(pIter);
 fts5BufferFree(&term);
 if( pnRem ) *pnRem -= writer.nLeafWritten;
}

/*
** If this is not a contentless_delete=1 table, or if the 'deletemerge'
** configuration option is set to 0, then this function always returns -1.
** Otherwise, it searches the structure object passed as the second argument
** for a level suitable for merging due to having a large number of
** tombstones in the tombstone hash. If one is found, its index is returned.
** Otherwise, if there is no suitable level, -1.
*/
static int fts5IndexFindDeleteMerge(Fts5Index *p, Fts5Structure *pStruct){
 Fts5Config *pConfig = p->pConfig;
 int iRet = -1;
 if( pConfig->bContentlessDelete && pConfig->nDeleteMerge>0 ){
 int ii;
 int nBest = 0;

 for(ii=0; ii<pStruct->nLevel; ii++){
 Fts5StructureLevel *pLvl = &pStruct->aLevel[ii];
 i64 nEntry = 0;
 i64 nTomb = 0;
 int iSeg;
 for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
 nEntry += pLvl->aSeg[iSeg].nEntry;
 nTomb += pLvl->aSeg[iSeg].nEntryTombstone;
 }
 assert_nc( nEntry>0 || pLvl->nSeg==0 );
 if( nEntry>0 ){
 int nPercent = (nTomb * 100) / nEntry;
 if( nPercent>=pConfig->nDeleteMerge && nPercent>nBest ){
 iRet = ii;
 nBest = nPercent;
 }
 }

 /* If pLvl is already the input level to an ongoing merge, look no
 ** further for a merge candidate. The caller should be allowed to
 ** continue merging from pLvl first. */
 if( pLvl->nMerge ) break;
 }
 }
 return iRet;
}

/*
** Do up to nPg pages of automerge work on the index.
**
** Return true if any changes were actually made, or false otherwise.
*/
static int fts5IndexMerge(
 Fts5Index *p, /* FTS5 backend object */
 Fts5Structure **ppStruct, /* IN/OUT: Current structure of index */
 int nPg, /* Pages of work to do */
 int nMin /* Minimum number of segments to merge */
){
 int nRem = nPg;
 int bRet = 0;
 Fts5Structure *pStruct = *ppStruct;
 while( nRem>0 && p->rc==SQLITE_OK ){
 int iLvl; /* To iterate through levels */
 int iBestLvl = 0; /* Level offering the most input segments */
 int nBest = 0; /* Number of input segments on best level */

 /* Set iBestLvl to the level to read input segments from. Or to -1 if
 ** there is no level suitable to merge segments from. */
 assert( pStruct->nLevel>0 );
 for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
 Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
 if( pLvl->nMerge ){
 if( pLvl->nMerge>nBest ){
 iBestLvl = iLvl;
 nBest = nMin;
 }
 break;
 }
 if( pLvl->nSeg>nBest ){
 nBest = pLvl->nSeg;
 iBestLvl = iLvl;
 }
 }
 if( nBest<nMin ){
 iBestLvl = fts5IndexFindDeleteMerge(p, pStruct);
 }

 if( iBestLvl<0 ) break;
 bRet = 1;
 fts5IndexMergeLevel(p, &pStruct, iBestLvl, &nRem);
 if( p->rc==SQLITE_OK && pStruct->aLevel[iBestLvl].nMerge==0 ){
 fts5StructurePromote(p, iBestLvl+1, pStruct);
 }

 if( nMin==1 ) nMin = 2;
 }
 *ppStruct = pStruct;
 return bRet;
}

/*
** A total of nLeaf leaf pages of data has just been flushed to a level-0
** segment. This function updates the write-counter accordingly and, if
** necessary, performs incremental merge work.
**
** If an error occurs, set the Fts5Index.rc error code. If an error has
** already occurred, this function is a no-op.
*/
static void fts5IndexAutomerge(
 Fts5Index *p, /* FTS5 backend object */
 Fts5Structure **ppStruct, /* IN/OUT: Current structure of index */
 int nLeaf /* Number of output leaves just written */
){
 if( p->rc==SQLITE_OK && p->pConfig->nAutomerge>0 && ALWAYS((*ppStruct)!=0) ){
 Fts5Structure *pStruct = *ppStruct;
 u64 nWrite; /* Initial value of write-counter */
 int nWork; /* Number of work-quanta to perform */
 int nRem; /* Number of leaf pages left to write */

 /* Update the write-counter. While doing so, set nWork. */
 nWrite = pStruct->nWriteCounter;
 nWork = (int)(((nWrite + nLeaf) / p->nWorkUnit) - (nWrite / p->nWorkUnit));
 pStruct->nWriteCounter += nLeaf;
 nRem = (int)(p->nWorkUnit * nWork * pStruct->nLevel);

 fts5IndexMerge(p, ppStruct, nRem, p->pConfig->nAutomerge);
 }
}

static void fts5IndexCrisismerge(
 Fts5Index *p, /* FTS5 backend object */
 Fts5Structure **ppStruct /* IN/OUT: Current structure of index */
){
 const int nCrisis = p->pConfig->nCrisisMerge;
 Fts5Structure *pStruct = *ppStruct;
 if( pStruct && pStruct->nLevel>0 ){
 int iLvl = 0;
 while( p->rc==SQLITE_OK && pStruct->aLevel[iLvl].nSeg>=nCrisis ){
 fts5IndexMergeLevel(p, &pStruct, iLvl, 0);
 assert( p->rc!=SQLITE_OK || pStruct->nLevel>(iLvl+1) );
 fts5StructurePromote(p, iLvl+1, pStruct);
 iLvl++;
 }
 *ppStruct = pStruct;
 }
}

static int fts5IndexReturn(Fts5Index *p){
 int rc = p->rc;
 p->rc = SQLITE_OK;
 return rc;
}

typedef struct Fts5FlushCtx Fts5FlushCtx;
struct Fts5FlushCtx {
 Fts5Index *pIdx;
 Fts5SegWriter writer;
};

/*
** Buffer aBuf[] contains a list of varints, all small enough to fit
** in a 32-bit integer. Return the size of the largest prefix of this
** list nMax bytes or less in size.
*/
static int fts5PoslistPrefix(const u8 *aBuf, int nMax){
 int ret;
 u32 dummy;
 ret = fts5GetVarint32(aBuf, dummy);
 if( ret<nMax ){
 while( 1 ){
 int i = fts5GetVarint32(&aBuf[ret], dummy);
 if( (ret + i) > nMax ) break;
 ret += i;
 }
 }
 return ret;
}

/*
** Execute the SQL statement:
**
** DELETE FROM %_idx WHERE (segid, (pgno/2)) = ($iSegid, $iPgno);
**
** This is used when a secure-delete operation removes the last term
** from a segment leaf page. In that case the %_idx entry is removed
** too. This is done to ensure that if all instances of a token are
** removed from an fts5 database in secure-delete mode, no trace of
** the token itself remains in the database.
*/
static void fts5SecureDeleteIdxEntry(
 Fts5Index *p, /* FTS5 backend object */
 int iSegid, /* Id of segment to delete entry for */
 int iPgno /* Page number within segment */
){
 if( iPgno!=1 ){
 assert( p->pConfig->iVersion==FTS5_CURRENT_VERSION_SECUREDELETE );
 if( p->pDeleteFromIdx==0 ){
 fts5IndexPrepareStmt(p, &p->pDeleteFromIdx, sqlite3_mprintf(
 "DELETE FROM '%q'.'%q_idx' WHERE (segid, (pgno/2)) = (?1, ?2)",
 p->pConfig->zDb, p->pConfig->zName
 ));
 }
 if( p->rc==SQLITE_OK ){
 sqlite3_bind_int(p->pDeleteFromIdx, 1, iSegid);
 sqlite3_bind_int(p->pDeleteFromIdx, 2, iPgno);
 sqlite3_step(p->pDeleteFromIdx);
 p->rc = sqlite3_reset(p->pDeleteFromIdx);
 }
 }
}

/*
** This is called when a secure-delete operation removes a position-list
** that overflows onto segment page iPgno of segment pSeg. This function
** rewrites node iPgno, and possibly one or more of its right-hand peers,
** to remove this portion of the position list.
**
** Output variable (*pbLastInDoclist) is set to true if the position-list
** removed is followed by a new term or the end-of-segment, or false if
** it is followed by another rowid/position list.
*/
static void fts5SecureDeleteOverflow(
 Fts5Index *p,
 Fts5StructureSegment *pSeg,
 int iPgno,
 int *pbLastInDoclist
){
 const int bDetailNone = (p->pConfig->eDetail==FTS5_DETAIL_NONE);
 int pgno;
 Fts5Data *pLeaf = 0;
 assert( iPgno!=1 );

 *pbLastInDoclist = 1;
 for(pgno=iPgno; p->rc==SQLITE_OK && pgno<=pSeg->pgnoLast; pgno++){
 i64 iRowid = FTS5_SEGMENT_ROWID(pSeg->iSegid, pgno);
 int iNext = 0;
 u8 *aPg = 0;

 pLeaf = fts5DataRead(p, iRowid);
 if( pLeaf==0 ) break;
 aPg = pLeaf->p;

 iNext = fts5GetU16(&aPg[0]);
 if( iNext!=0 ){
 *pbLastInDoclist = 0;
 }
 if( iNext==0 && pLeaf->szLeaf!=pLeaf->nn ){
 fts5GetVarint32(&aPg[pLeaf->szLeaf], iNext);
 }

 if( iNext==0 ){
 /* The page contains no terms or rowids. Replace it with an empty
 ** page and move on to the right-hand peer. */
 const u8 aEmpty[] = {0x00, 0x00, 0x00, 0x04};
 assert_nc( bDetailNone==0 || pLeaf->nn==4 );
 if( bDetailNone==0 ) fts5DataWrite(p, iRowid, aEmpty, sizeof(aEmpty));
 fts5DataRelease(pLeaf);
 pLeaf = 0;
 }else if( bDetailNone ){
 break;
 }else if( iNext>=pLeaf->szLeaf || pLeaf->nn<pLeaf->szLeaf || iNext<4 ){
 p->rc = FTS5_CORRUPT;
 break;
 }else{
 int nShift = iNext - 4;
 int nPg;

 int nIdx = 0;
 u8 *aIdx = 0;

 /* Unless the current page footer is 0 bytes in size (in which case
 ** the new page footer will be as well), allocate and populate a
 ** buffer containing the new page footer. Set stack variables aIdx
 ** and nIdx accordingly. */
 if( pLeaf->nn>pLeaf->szLeaf ){
 int iFirst = 0;
 int i1 = pLeaf->szLeaf;
 int i2 = 0;

 i1 += fts5GetVarint32(&aPg[i1], iFirst);
 if( iFirst<iNext ){
 p->rc = FTS5_CORRUPT;
 break;
 }
 aIdx = sqlite3Fts5MallocZero(&p->rc, (pLeaf->nn-pLeaf->szLeaf)+2);
 if( aIdx==0 ) break;
 i2 = sqlite3Fts5PutVarint(aIdx, iFirst-nShift);
 if( i1<pLeaf->nn ){
 memcpy(&aIdx[i2], &aPg[i1], pLeaf->nn-i1);
 i2 += (pLeaf->nn-i1);
 }
 nIdx = i2;
 }

 /* Modify the contents of buffer aPg[]. Set nPg to the new size
 ** in bytes. The new page is always smaller than the old. */
 nPg = pLeaf->szLeaf - nShift;
 memmove(&aPg[4], &aPg[4+nShift], nPg-4);
 fts5PutU16(&aPg[2], nPg);
 if( fts5GetU16(&aPg[0]) ) fts5PutU16(&aPg[0], 4);
 if( nIdx>0 ){
 memcpy(&aPg[nPg], aIdx, nIdx);
 nPg += nIdx;
 }
 sqlite3_free(aIdx);

 /* Write the new page to disk and exit the loop */
 assert( nPg>4 || fts5GetU16(aPg)==0 );
 fts5DataWrite(p, iRowid, aPg, nPg);
 break;
 }
 }
 fts5DataRelease(pLeaf);
}

/*
** Completely remove the entry that pSeg currently points to from
** the database.
*/
static void fts5DoSecureDelete(
 Fts5Index *p,
 Fts5SegIter *pSeg
){
 const int bDetailNone = (p->pConfig->eDetail==FTS5_DETAIL_NONE);
 int iSegid = pSeg->pSeg->iSegid;
 u8 *aPg = pSeg->pLeaf->p;
 int nPg = pSeg->pLeaf->nn;
 int iPgIdx = pSeg->pLeaf->szLeaf;

 u64 iDelta = 0;
 int iNextOff = 0;
 int iOff = 0;
 int nIdx = 0;
 u8 *aIdx = 0;
 int bLastInDoclist = 0;
 int iIdx = 0;
 int iStart = 0;
 int iDelKeyOff = 0; /* Offset of deleted key, if any */

 nIdx = nPg-iPgIdx;
 aIdx = sqlite3Fts5MallocZero(&p->rc, nIdx+16);
 if( p->rc ) return;
 memcpy(aIdx, &aPg[iPgIdx], nIdx);

 /* At this point segment iterator pSeg points to the entry
 ** this function should remove from the b-tree segment.
 **
 ** In detail=full or detail=column mode, pSeg->iLeafOffset is the
 ** offset of the first byte in the position-list for the entry to
 ** remove. Immediately before this comes two varints that will also
 ** need to be removed:
 **
 ** + the rowid or delta rowid value for the entry, and
 ** + the size of the position list in bytes.
 **
 ** Or, in detail=none mode, there is a single varint prior to
 ** pSeg->iLeafOffset - the rowid or delta rowid value.
 **
 ** This block sets the following variables:
 **
 ** iStart:
 ** The offset of the first byte of the rowid or delta-rowid
 ** value for the doclist entry being removed.
 **
 ** iDelta:
 ** The value of the rowid or delta-rowid value for the doclist
 ** entry being removed.
 **
 ** iNextOff:
 ** The offset of the next entry following the position list
 ** for the one being removed. If the position list for this
 ** entry overflows onto the next leaf page, this value will be
 ** greater than pLeaf->szLeaf.
 */
 {
 int iSOP; /* Start-Of-Position-list */
 if( pSeg->iLeafPgno==pSeg->iTermLeafPgno ){
 iStart = pSeg->iTermLeafOffset;
 }else{
 iStart = fts5GetU16(&aPg[0]);
 }

 iSOP = iStart + fts5GetVarint(&aPg[iStart], &iDelta);
 assert_nc( iSOP<=pSeg->iLeafOffset );

 if( bDetailNone ){
 while( iSOP<pSeg->iLeafOffset ){
 if( aPg[iSOP]==0x00 ) iSOP++;
 if( aPg[iSOP]==0x00 ) iSOP++;
 iStart = iSOP;
 iSOP = iStart + fts5GetVarint(&aPg[iStart], &iDelta);
 }

 iNextOff = iSOP;
 if( iNextOff<pSeg->iEndofDoclist && aPg[iNextOff]==0x00 ) iNextOff++;
 if( iNextOff<pSeg->iEndofDoclist && aPg[iNextOff]==0x00 ) iNextOff++;

 }else{
 int nPos = 0;
 iSOP += fts5GetVarint32(&aPg[iSOP], nPos);
 while( iSOP<pSeg->iLeafOffset ){
 iStart = iSOP + (nPos/2);
 iSOP = iStart + fts5GetVarint(&aPg[iStart], &iDelta);
 iSOP += fts5GetVarint32(&aPg[iSOP], nPos);
 }
 assert_nc( iSOP==pSeg->iLeafOffset );
 iNextOff = pSeg->iLeafOffset + pSeg->nPos;
 }
 }

 iOff = iStart;

 /* If the position-list for the entry being removed flows over past
 ** the end of this page, delete the portion of the position-list on the
 ** next page and beyond.
 **
 ** Set variable bLastInDoclist to true if this entry happens
 ** to be the last rowid in the doclist for its term. */
 if( iNextOff>=iPgIdx ){
 int pgno = pSeg->iLeafPgno+1;
 fts5SecureDeleteOverflow(p, pSeg->pSeg, pgno, &bLastInDoclist);
 iNextOff = iPgIdx;
 }

 if( pSeg->bDel==0 ){
 if( iNextOff!=iPgIdx ){
 /* Loop through the page-footer. If iNextOff (offset of the
 ** entry following the one we are removing) is equal to the
 ** offset of a key on this page, then the entry is the last
 ** in its doclist. */
 int iKeyOff = 0;
 for(iIdx=0; iIdx<nIdx; /* no-op */){
 u32 iVal = 0;
 iIdx += fts5GetVarint32(&aIdx[iIdx], iVal);
 iKeyOff += iVal;
 if( iKeyOff==iNextOff ){
 bLastInDoclist = 1;
 }
 }
 }

 /* If this is (a) the first rowid on a page and (b) is not followed by
 ** another position list on the same page, set the "first-rowid" field
 ** of the header to 0. */
 if( fts5GetU16(&aPg[0])==iStart && (bLastInDoclist || iNextOff==iPgIdx) ){
 fts5PutU16(&aPg[0], 0);
 }
 }

 if( pSeg->bDel ){
 iOff += sqlite3Fts5PutVarint(&aPg[iOff], iDelta);
 aPg[iOff++] = 0x01;
 }else if( bLastInDoclist==0 ){
 if( iNextOff!=iPgIdx ){
 u64 iNextDelta = 0;
 iNextOff += fts5GetVarint(&aPg[iNextOff], &iNextDelta);
 iOff += sqlite3Fts5PutVarint(&aPg[iOff], iDelta + iNextDelta);
 }
 }else if(
 pSeg->iLeafPgno==pSeg->iTermLeafPgno
 && iStart==pSeg->iTermLeafOffset
 ){
 /* The entry being removed was the only position list in its
 ** doclist. Therefore the term needs to be removed as well. */
 int iKey = 0;
 int iKeyOff = 0;

 /* Set iKeyOff to the offset of the term that will be removed - the
 ** last offset in the footer that is not greater than iStart. */
 for(iIdx=0; iIdx<nIdx; iKey++){
 u32 iVal = 0;
 iIdx += fts5GetVarint32(&aIdx[iIdx], iVal);
 if( (iKeyOff+iVal)>(u32)iStart ) break;
 iKeyOff += iVal;
 }
 assert_nc( iKey>=1 );

 /* Set iDelKeyOff to the value of the footer entry to remove from
 ** the page. */
 iDelKeyOff = iOff = iKeyOff;

 if( iNextOff!=iPgIdx ){
 /* This is the only position-list associated with the term, and there
 ** is another term following it on this page. So the subsequent term
 ** needs to be moved to replace the term associated with the entry
 ** being removed. */
 int nPrefix = 0;
 int nSuffix = 0;
 int nPrefix2 = 0;
 int nSuffix2 = 0;

 iDelKeyOff = iNextOff;
 iNextOff += fts5GetVarint32(&aPg[iNextOff], nPrefix2);
 iNextOff += fts5GetVarint32(&aPg[iNextOff], nSuffix2);

 if( iKey!=1 ){
 iKeyOff += fts5GetVarint32(&aPg[iKeyOff], nPrefix);
 }
 iKeyOff += fts5GetVarint32(&aPg[iKeyOff], nSuffix);

 nPrefix = MIN(nPrefix, nPrefix2);
 nSuffix = (nPrefix2 + nSuffix2) - nPrefix;

 if( (iKeyOff+nSuffix)>iPgIdx || (iNextOff+nSuffix2)>iPgIdx ){
 p->rc = FTS5_CORRUPT;
 }else{
 if( iKey!=1 ){
 iOff += sqlite3Fts5PutVarint(&aPg[iOff], nPrefix);
 }
 iOff += sqlite3Fts5PutVarint(&aPg[iOff], nSuffix);
 if( nPrefix2>pSeg->term.n ){
 p->rc = FTS5_CORRUPT;
 }else if( nPrefix2>nPrefix ){
 memcpy(&aPg[iOff], &pSeg->term.p[nPrefix], nPrefix2-nPrefix);
 iOff += (nPrefix2-nPrefix);
 }
 memmove(&aPg[iOff], &aPg[iNextOff], nSuffix2);
 iOff += nSuffix2;
 iNextOff += nSuffix2;
 }
 }
 }else if( iStart==4 ){
 int iPgno;

 assert_nc( pSeg->iLeafPgno>pSeg->iTermLeafPgno );
 /* The entry being removed may be the only position list in
 ** its doclist. */
 for(iPgno=pSeg->iLeafPgno-1; iPgno>pSeg->iTermLeafPgno; iPgno-- ){
 Fts5Data *pPg = fts5DataRead(p, FTS5_SEGMENT_ROWID(iSegid, iPgno));
 int bEmpty = (pPg && pPg->nn==4);
 fts5DataRelease(pPg);
 if( bEmpty==0 ) break;
 }

 if( iPgno==pSeg->iTermLeafPgno ){
 i64 iId = FTS5_SEGMENT_ROWID(iSegid, pSeg->iTermLeafPgno);
 Fts5Data *pTerm = fts5DataRead(p, iId);
 if( pTerm && pTerm->szLeaf==pSeg->iTermLeafOffset ){
 u8 *aTermIdx = &pTerm->p[pTerm->szLeaf];
 int nTermIdx = pTerm->nn - pTerm->szLeaf;
 int iTermIdx = 0;
 int iTermOff = 0;

 while( 1 ){
 u32 iVal = 0;
 int nByte = fts5GetVarint32(&aTermIdx[iTermIdx], iVal);
 iTermOff += iVal;
 if( (iTermIdx+nByte)>=nTermIdx ) break;
 iTermIdx += nByte;
 }
 nTermIdx = iTermIdx;

 memmove(&pTerm->p[iTermOff], &pTerm->p[pTerm->szLeaf], nTermIdx);
 fts5PutU16(&pTerm->p[2], iTermOff);

 fts5DataWrite(p, iId, pTerm->p, iTermOff+nTermIdx);
 if( nTermIdx==0 ){
 fts5SecureDeleteIdxEntry(p, iSegid, pSeg->iTermLeafPgno);
 }
 }
 fts5DataRelease(pTerm);
 }
 }

 /* Assuming no error has occurred, this block does final edits to the
 ** leaf page before writing it back to disk. Input variables are:
 **
 ** nPg: Total initial size of leaf page.
 ** iPgIdx: Initial offset of page footer.
 **
 ** iOff: Offset to move data to
 ** iNextOff: Offset to move data from
 */
 if( p->rc==SQLITE_OK ){
 const int nMove = nPg - iNextOff; /* Number of bytes to move */
 int nShift = iNextOff - iOff; /* Distance to move them */

 int iPrevKeyOut = 0;
 int iKeyIn = 0;

 memmove(&aPg[iOff], &aPg[iNextOff], nMove);
 iPgIdx -= nShift;
 nPg = iPgIdx;
 fts5PutU16(&aPg[2], iPgIdx);

 for(iIdx=0; iIdx<nIdx; /* no-op */){
 u32 iVal = 0;
 iIdx += fts5GetVarint32(&aIdx[iIdx], iVal);
 iKeyIn += iVal;
 if( iKeyIn!=iDelKeyOff ){
 int iKeyOut = (iKeyIn - (iKeyIn>iOff ? nShift : 0));
 nPg += sqlite3Fts5PutVarint(&aPg[nPg], iKeyOut - iPrevKeyOut);
 iPrevKeyOut = iKeyOut;
 }
 }

 if( iPgIdx==nPg && nIdx>0 && pSeg->iLeafPgno!=1 ){
 fts5SecureDeleteIdxEntry(p, iSegid, pSeg->iLeafPgno);
 }

 assert_nc( nPg>4 || fts5GetU16(aPg)==0 );
 fts5DataWrite(p, FTS5_SEGMENT_ROWID(iSegid,pSeg->iLeafPgno), aPg, nPg);
 }
 sqlite3_free(aIdx);
}

/*
** This is called as part of flushing a delete to disk in 'secure-delete'
** mode. It edits the segments within the database described by argument
** pStruct to remove the entries for term zTerm, rowid iRowid.
*/
static void fts5FlushSecureDelete(
 Fts5Index *p,
 Fts5Structure *pStruct,
 const char *zTerm,
 int nTerm,
 i64 iRowid
){
 const int f = FTS5INDEX_QUERY_SKIPHASH;
 Fts5Iter *pIter = 0; /* Used to find term instance */

 fts5MultiIterNew(p, pStruct, f, 0, (const u8*)zTerm, nTerm, -1, 0, &pIter);
 if( fts5MultiIterEof(p, pIter)==0 ){
 i64 iThis = fts5MultiIterRowid(pIter);
 if( iThis<iRowid ){
 fts5MultiIterNextFrom(p, pIter, iRowid);
 }

 if( p->rc==SQLITE_OK
 && fts5MultiIterEof(p, pIter)==0
 && iRowid==fts5MultiIterRowid(pIter)
 ){
 Fts5SegIter *pSeg = &pIter->aSeg[pIter->aFirst[1].iFirst];
 fts5DoSecureDelete(p, pSeg);
 }
 }

 fts5MultiIterFree(pIter);
}

/*
** Flush the contents of in-memory hash table iHash to a new level-0
** segment on disk. Also update the corresponding structure record.
**
** If an error occurs, set the Fts5Index.rc error code. If an error has
** already occurred, this function is a no-op.
*/
static void fts5FlushOneHash(Fts5Index *p){
 Fts5Hash *pHash = p->pHash;
 Fts5Structure *pStruct;
 int iSegid;
 int pgnoLast = 0; /* Last leaf page number in segment */

 /* Obtain a reference to the index structure and allocate a new segment-id
 ** for the new level-0 segment. */
 pStruct = fts5StructureRead(p);
 fts5StructureInvalidate(p);

 if( sqlite3Fts5HashIsEmpty(pHash)==0 ){
 iSegid = fts5AllocateSegid(p, pStruct);
 if( iSegid ){
 const int pgsz = p->pConfig->pgsz;
 int eDetail = p->pConfig->eDetail;
 int bSecureDelete = p->pConfig->bSecureDelete;
 Fts5StructureSegment *pSeg; /* New segment within pStruct */
 Fts5Buffer *pBuf; /* Buffer in which to assemble leaf page */
 Fts5Buffer *pPgidx; /* Buffer in which to assemble pgidx */

 Fts5SegWriter writer;
 fts5WriteInit(p, &writer, iSegid);

 pBuf = &writer.writer.buf;
 pPgidx = &writer.writer.pgidx;

 /* fts5WriteInit() should have initialized the buffers to (most likely)
 ** the maximum space required. */
 assert( p->rc || pBuf->nSpace>=(pgsz + FTS5_DATA_PADDING) );
 assert( p->rc || pPgidx->nSpace>=(pgsz + FTS5_DATA_PADDING) );

 /* Begin scanning through hash table entries. This loop runs once for each
 ** term/doclist currently stored within the hash table. */
 if( p->rc==SQLITE_OK ){
 p->rc = sqlite3Fts5HashScanInit(pHash, 0, 0);
 }
 while( p->rc==SQLITE_OK && 0==sqlite3Fts5HashScanEof(pHash) ){
 const char *zTerm; /* Buffer containing term */
 int nTerm; /* Size of zTerm in bytes */
 const u8 *pDoclist; /* Pointer to doclist for this term */
 int nDoclist; /* Size of doclist in bytes */

 /* Get the term and doclist for this entry. */
 sqlite3Fts5HashScanEntry(pHash, &zTerm, &nTerm, &pDoclist, &nDoclist);
 if( bSecureDelete==0 ){
 fts5WriteAppendTerm(p, &writer, nTerm, (const u8*)zTerm);
 if( p->rc!=SQLITE_OK ) break;
 assert( writer.bFirstRowidInPage==0 );
 }

 if( !bSecureDelete && pgsz>=(pBuf->n + pPgidx->n + nDoclist + 1) ){
 /* The entire doclist will fit on the current leaf. */
 fts5BufferSafeAppendBlob(pBuf, pDoclist, nDoclist);
 }else{
 int bTermWritten = !bSecureDelete;
 i64 iRowid = 0;
 i64 iPrev = 0;
 int iOff = 0;

 /* The entire doclist will not fit on this leaf. The following
 ** loop iterates through the poslists that make up the current
 ** doclist. */
 while( p->rc==SQLITE_OK && iOff<nDoclist ){
 u64 iDelta = 0;
 iOff += fts5GetVarint(&pDoclist[iOff], &iDelta);
 iRowid += iDelta;

 /* If in secure delete mode, and if this entry in the poslist is
 ** in fact a delete, then edit the existing segments directly
 ** using fts5FlushSecureDelete(). */
 if( bSecureDelete ){
 if( eDetail==FTS5_DETAIL_NONE ){
 if( iOff<nDoclist && pDoclist[iOff]==0x00 ){
 fts5FlushSecureDelete(p, pStruct, zTerm, nTerm, iRowid);
 iOff++;
 if( iOff<nDoclist && pDoclist[iOff]==0x00 ){
 iOff++;
 nDoclist = 0;
 }else{
 continue;
 }
 }
 }else if( (pDoclist[iOff] & 0x01) ){
 fts5FlushSecureDelete(p, pStruct, zTerm, nTerm, iRowid);
 if( p->rc!=SQLITE_OK || pDoclist[iOff]==0x01 ){
 iOff++;
 continue;
 }
 }
 }

 if( p->rc==SQLITE_OK && bTermWritten==0 ){
 fts5WriteAppendTerm(p, &writer, nTerm, (const u8*)zTerm);
 bTermWritten = 1;
 assert( p->rc!=SQLITE_OK || writer.bFirstRowidInPage==0 );
 }

 if( writer.bFirstRowidInPage ){
 fts5PutU16(&pBuf->p[0], (u16)pBuf->n); /* first rowid on page */
 pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iRowid);
 writer.bFirstRowidInPage = 0;
 fts5WriteDlidxAppend(p, &writer, iRowid);
 }else{
 u64 iRowidDelta = (u64)iRowid - (u64)iPrev;
 pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iRowidDelta);
 }
 if( p->rc!=SQLITE_OK ) break;
 assert( pBuf->n<=pBuf->nSpace );
 iPrev = iRowid;

 if( eDetail==FTS5_DETAIL_NONE ){
 if( iOff<nDoclist && pDoclist[iOff]==0 ){
 pBuf->p[pBuf->n++] = 0;
 iOff++;
 if( iOff<nDoclist && pDoclist[iOff]==0 ){
 pBuf->p[pBuf->n++] = 0;
 iOff++;
 }
 }
 if( (pBuf->n + pPgidx->n)>=pgsz ){
 fts5WriteFlushLeaf(p, &writer);
 }
 }else{
 int bDel = 0;
 int nPos = 0;
 int nCopy = fts5GetPoslistSize(&pDoclist[iOff], &nPos, &bDel);
 if( bDel && bSecureDelete ){
 fts5BufferAppendVarint(&p->rc, pBuf, nPos*2);
 iOff += nCopy;
 nCopy = nPos;
 }else{
 nCopy += nPos;
 }
 if( (pBuf->n + pPgidx->n + nCopy) <= pgsz ){
 /* The entire poslist will fit on the current leaf. So copy
 ** it in one go. */
 fts5BufferSafeAppendBlob(pBuf, &pDoclist[iOff], nCopy);
 }else{
 /* The entire poslist will not fit on this leaf. So it needs
 ** to be broken into sections. The only qualification being
 ** that each varint must be stored contiguously. */
 const u8 *pPoslist = &pDoclist[iOff];
 int iPos = 0;
 while( p->rc==SQLITE_OK ){
 int nSpace = pgsz - pBuf->n - pPgidx->n;
 int n = 0;
 if( (nCopy - iPos)<=nSpace ){
 n = nCopy - iPos;
 }else{
 n = fts5PoslistPrefix(&pPoslist[iPos], nSpace);
 }
 assert( n>0 );
 fts5BufferSafeAppendBlob(pBuf, &pPoslist[iPos], n);
 iPos += n;
 if( (pBuf->n + pPgidx->n)>=pgsz ){
 fts5WriteFlushLeaf(p, &writer);
 }
 if( iPos>=nCopy ) break;
 }
 }
 iOff += nCopy;
 }
 }
 }

 /* TODO2: Doclist terminator written here. */
 /* pBuf->p[pBuf->n++] = '\0'; */
 assert( pBuf->n<=pBuf->nSpace );
 if( p->rc==SQLITE_OK ) sqlite3Fts5HashScanNext(pHash);
 }
 fts5WriteFinish(p, &writer, &pgnoLast);

 assert( p->rc!=SQLITE_OK || bSecureDelete || pgnoLast>0 );
 if( pgnoLast>0 ){
 /* Update the Fts5Structure. It is written back to the database by the
 ** fts5StructureRelease() call below. */
 if( pStruct->nLevel==0 ){
 fts5StructureAddLevel(&p->rc, &pStruct);
 }
 fts5StructureExtendLevel(&p->rc, pStruct, 0, 1, 0);
 if( p->rc==SQLITE_OK ){
 pSeg = &pStruct->aLevel[0].aSeg[ pStruct->aLevel[0].nSeg++ ];
 pSeg->iSegid = iSegid;
 pSeg->pgnoFirst = 1;
 pSeg->pgnoLast = pgnoLast;
 if( pStruct->nOriginCntr>0 ){
 pSeg->iOrigin1 = pStruct->nOriginCntr;
 pSeg->iOrigin2 = pStruct->nOriginCntr;
 pSeg->nEntry = p->nPendingRow;
 pStruct->nOriginCntr++;
 }
 pStruct->nSegment++;
 }
 fts5StructurePromote(p, 0, pStruct);
 }
 }
 }

 fts5IndexAutomerge(p, &pStruct, pgnoLast + p->nContentlessDelete);
 fts5IndexCrisismerge(p, &pStruct);
 fts5StructureWrite(p, pStruct);
 fts5StructureRelease(pStruct);
}

/*
** Flush any data stored in the in-memory hash tables to the database.
*/
static void fts5IndexFlush(Fts5Index *p){
 /* Unless it is empty, flush the hash table to disk */
 if( p->flushRc ){
 p->rc = p->flushRc;
 return;
 }
 if( p->nPendingData || p->nContentlessDelete ){
 assert( p->pHash );
 fts5FlushOneHash(p);
 if( p->rc==SQLITE_OK ){
 sqlite3Fts5HashClear(p->pHash);
 p->nPendingData = 0;
 p->nPendingRow = 0;
 p->nContentlessDelete = 0;
 }else if( p->nPendingData || p->nContentlessDelete ){
 p->flushRc = p->rc;
 }
 }
}

static Fts5Structure *fts5IndexOptimizeStruct(
 Fts5Index *p,
 Fts5Structure *pStruct
){
 Fts5Structure *pNew = 0;
 sqlite3_int64 nByte = sizeof(Fts5Structure);
 int nSeg = pStruct->nSegment;
 int i;

 /* Figure out if this structure requires optimization. A structure does
 ** not require optimization if either:
 **
 ** 1. it consists of fewer than two segments, or
 ** 2. all segments are on the same level, or
 ** 3. all segments except one are currently inputs to a merge operation.
 **
 ** In the first case, if there are no tombstone hash pages, return NULL. In
 ** the second, increment the ref-count on *pStruct and return a copy of the
 ** pointer to it.
 */
 if( nSeg==0 ) return 0;
 for(i=0; i<pStruct->nLevel; i++){
 int nThis = pStruct->aLevel[i].nSeg;
 int nMerge = pStruct->aLevel[i].nMerge;
 if( nThis>0 && (nThis==nSeg || (nThis==nSeg-1 && nMerge==nThis)) ){
 if( nSeg==1 && nThis==1 && pStruct->aLevel[i].aSeg[0].nPgTombstone==0 ){
 return 0;
 }
 fts5StructureRef(pStruct);
 return pStruct;
 }
 assert( pStruct->aLevel[i].nMerge<=nThis );
 }

 nByte += (pStruct->nLevel+1) * sizeof(Fts5StructureLevel);
 pNew = (Fts5Structure*)sqlite3Fts5MallocZero(&p->rc, nByte);

 if( pNew ){
 Fts5StructureLevel *pLvl;
 nByte = nSeg * sizeof(Fts5StructureSegment);
 pNew->nLevel = MIN(pStruct->nLevel+1, FTS5_MAX_LEVEL);
 pNew->nRef = 1;
 pNew->nWriteCounter = pStruct->nWriteCounter;
 pNew->nOriginCntr = pStruct->nOriginCntr;
 pLvl = &pNew->aLevel[pNew->nLevel-1];
 pLvl->aSeg = (Fts5StructureSegment*)sqlite3Fts5MallocZero(&p->rc, nByte);
 if( pLvl->aSeg ){
 int iLvl, iSeg;
 int iSegOut = 0;
 /* Iterate through all segments, from oldest to newest. Add them to
 ** the new Fts5Level object so that pLvl->aSeg[0] is the oldest
 ** segment in the data structure. */
 for(iLvl=pStruct->nLevel-1; iLvl>=0; iLvl--){
 for(iSeg=0; iSeg<pStruct->aLevel[iLvl].nSeg; iSeg++){
 pLvl->aSeg[iSegOut] = pStruct->aLevel[iLvl].aSeg[iSeg];
 iSegOut++;
 }
 }
 pNew->nSegment = pLvl->nSeg = nSeg;
 }else{
 sqlite3_free(pNew);
 pNew = 0;
 }
 }

 return pNew;
}

static int sqlite3Fts5IndexOptimize(Fts5Index *p){
 Fts5Structure *pStruct;
 Fts5Structure *pNew = 0;

 assert( p->rc==SQLITE_OK );
 fts5IndexFlush(p);
 assert( p->rc!=SQLITE_OK || p->nContentlessDelete==0 );
 pStruct = fts5StructureRead(p);
 assert( p->rc!=SQLITE_OK || pStruct!=0 );
 fts5StructureInvalidate(p);

 if( pStruct ){
 pNew = fts5IndexOptimizeStruct(p, pStruct);
 }
 fts5StructureRelease(pStruct);

 assert( pNew==0 || pNew->nSegment>0 );
 if( pNew ){
 int iLvl;
 for(iLvl=0; pNew->aLevel[iLvl].nSeg==0; iLvl++){}
 while( p->rc==SQLITE_OK && pNew->aLevel[iLvl].nSeg>0 ){
 int nRem = FTS5_OPT_WORK_UNIT;
 fts5IndexMergeLevel(p, &pNew, iLvl, &nRem);
 }

 fts5StructureWrite(p, pNew);
 fts5StructureRelease(pNew);
 }

 return fts5IndexReturn(p);
}

/*
** This is called to implement the special "VALUES('merge', $nMerge)"
** INSERT command.
*/
static int sqlite3Fts5IndexMerge(Fts5Index *p, int nMerge){
 Fts5Structure *pStruct = 0;

 fts5IndexFlush(p);
 pStruct = fts5StructureRead(p);
 if( pStruct ){
 int nMin = p->pConfig->nUsermerge;
 fts5StructureInvalidate(p);
 if( nMerge<0 ){
 Fts5Structure *pNew = fts5IndexOptimizeStruct(p, pStruct);
 fts5StructureRelease(pStruct);
 pStruct = pNew;
 nMin = 1;
 nMerge = nMerge*-1;
 }
 if( pStruct && pStruct->nLevel ){
 if( fts5IndexMerge(p, &pStruct, nMerge, nMin) ){
 fts5StructureWrite(p, pStruct);
 }
 }
 fts5StructureRelease(pStruct);
 }
 return fts5IndexReturn(p);
}

static void fts5AppendRowid(
 Fts5Index *p,
 u64 iDelta,
 Fts5Iter *pUnused,
 Fts5Buffer *pBuf
){
 UNUSED_PARAM(pUnused);
 fts5BufferAppendVarint(&p->rc, pBuf, iDelta);
}

static void fts5AppendPoslist(
 Fts5Index *p,
 u64 iDelta,
 Fts5Iter *pMulti,
 Fts5Buffer *pBuf
){
 int nData = pMulti->base.nData;
 int nByte = nData + 9 + 9 + FTS5_DATA_ZERO_PADDING;
 assert( nData>0 );
 if( p->rc==SQLITE_OK && 0==fts5BufferGrow(&p->rc, pBuf, nByte) ){
 fts5BufferSafeAppendVarint(pBuf, iDelta);
 fts5BufferSafeAppendVarint(pBuf, nData*2);
 fts5BufferSafeAppendBlob(pBuf, pMulti->base.pData, nData);
 memset(&pBuf->p[pBuf->n], 0, FTS5_DATA_ZERO_PADDING);
 }
}

static void fts5DoclistIterNext(Fts5DoclistIter *pIter){
 u8 *p = pIter->aPoslist + pIter->nSize + pIter->nPoslist;

 assert( pIter->aPoslist || (p==0 && pIter->aPoslist==0) );
 if( p>=pIter->aEof ){
 pIter->aPoslist = 0;
 }else{
 i64 iDelta;

 p += fts5GetVarint(p, (u64*)&iDelta);
 pIter->iRowid += iDelta;

 /* Read position list size */
 if( p[0] & 0x80 ){
 int nPos;
 pIter->nSize = fts5GetVarint32(p, nPos);
 pIter->nPoslist = (nPos>>1);
 }else{
 pIter->nPoslist = ((int)(p[0])) >> 1;
 pIter->nSize = 1;
 }

 pIter->aPoslist = p;
 if( &pIter->aPoslist[pIter->nPoslist]>pIter->aEof ){
 pIter->aPoslist = 0;
 }
 }
}

static void fts5DoclistIterInit(
 Fts5Buffer *pBuf,
 Fts5DoclistIter *pIter
){
 memset(pIter, 0, sizeof(*pIter));
 if( pBuf->n>0 ){
 pIter->aPoslist = pBuf->p;
 pIter->aEof = &pBuf->p[pBuf->n];
 fts5DoclistIterNext(pIter);
 }
}

#if 0
/*
** Append a doclist to buffer pBuf.
**
** This function assumes that space within the buffer has already been
** allocated.
*/
static void fts5MergeAppendDocid(
 Fts5Buffer *pBuf, /* Buffer to write to */
 i64 *piLastRowid, /* IN/OUT: Previous rowid written (if any) */
 i64 iRowid /* Rowid to append */
){
 assert( pBuf->n!=0 || (*piLastRowid)==0 );
 fts5BufferSafeAppendVarint(pBuf, iRowid - *piLastRowid);
 *piLastRowid = iRowid;
}
#endif

#define fts5MergeAppendDocid(pBuf, iLastRowid, iRowid) { \
 assert( (pBuf)->n!=0 || (iLastRowid)==0 ); \
 fts5BufferSafeAppendVarint((pBuf), (u64)(iRowid) - (u64)(iLastRowid)); \
 (iLastRowid) = (iRowid); \
}

/*
** Swap the contents of buffer *p1 with that of *p2.
*/
static void fts5BufferSwap(Fts5Buffer *p1, Fts5Buffer *p2){
 Fts5Buffer tmp = *p1;
 *p1 = *p2;
 *p2 = tmp;
}

static void fts5NextRowid(Fts5Buffer *pBuf, int *piOff, i64 *piRowid){
 int i = *piOff;
 if( i>=pBuf->n ){
 *piOff = -1;
 }else{
 u64 iVal;
 *piOff = i + sqlite3Fts5GetVarint(&pBuf->p[i], &iVal);
 *piRowid += iVal;
 }
}

/*
** This is the equivalent of fts5MergePrefixLists() for detail=none mode.
** In this case the buffers consist of a delta-encoded list of rowids only.
*/
static void fts5MergeRowidLists(
 Fts5Index *p, /* FTS5 backend object */
 Fts5Buffer *p1, /* First list to merge */
 int nBuf, /* Number of entries in apBuf[] */
 Fts5Buffer *aBuf /* Array of other lists to merge into p1 */
){
 int i1 = 0;
 int i2 = 0;
 i64 iRowid1 = 0;
 i64 iRowid2 = 0;
 i64 iOut = 0;
 Fts5Buffer *p2 = &aBuf[0];
 Fts5Buffer out;

 (void)nBuf;
 memset(&out, 0, sizeof(out));
 assert( nBuf==1 );
 sqlite3Fts5BufferSize(&p->rc, &out, p1->n + p2->n);
 if( p->rc ) return;

 fts5NextRowid(p1, &i1, &iRowid1);
 fts5NextRowid(p2, &i2, &iRowid2);
 while( i1>=0 || i2>=0 ){
 if( i1>=0 && (i2<0 || iRowid1<iRowid2) ){
 assert( iOut==0 || iRowid1>iOut );
 fts5BufferSafeAppendVarint(&out, iRowid1 - iOut);
 iOut = iRowid1;
 fts5NextRowid(p1, &i1, &iRowid1);
 }else{
 assert( iOut==0 || iRowid2>iOut );
 fts5BufferSafeAppendVarint(&out, iRowid2 - iOut);
 iOut = iRowid2;
 if( i1>=0 && iRowid1==iRowid2 ){
 fts5NextRowid(p1, &i1, &iRowid1);
 }
 fts5NextRowid(p2, &i2, &iRowid2);
 }
 }

 fts5BufferSwap(&out, p1);
 fts5BufferFree(&out);
}

typedef struct PrefixMerger PrefixMerger;
struct PrefixMerger {
 Fts5DoclistIter iter; /* Doclist iterator */
 i64 iPos; /* For iterating through a position list */
 int iOff;
 u8 *aPos;
 PrefixMerger *pNext; /* Next in docid/poslist order */
};

static void fts5PrefixMergerInsertByRowid(
 PrefixMerger **ppHead,
 PrefixMerger *p
){
 if( p->iter.aPoslist ){
 PrefixMerger **pp = ppHead;
 while( *pp && p->iter.iRowid>(*pp)->iter.iRowid ){
 pp = &(*pp)->pNext;
 }
 p->pNext = *pp;
 *pp = p;
 }
}

static void fts5PrefixMergerInsertByPosition(
 PrefixMerger **ppHead,
 PrefixMerger *p
){
 if( p->iPos>=0 ){
 PrefixMerger **pp = ppHead;
 while( *pp && p->iPos>(*pp)->iPos ){
 pp = &(*pp)->pNext;
 }
 p->pNext = *pp;
 *pp = p;
 }
}

/*
** Array aBuf[] contains nBuf doclists. These are all merged in with the
** doclist in buffer p1.
*/
static void fts5MergePrefixLists(
 Fts5Index *p, /* FTS5 backend object */
 Fts5Buffer *p1, /* First list to merge */
 int nBuf, /* Number of buffers in array aBuf[] */
 Fts5Buffer *aBuf /* Other lists to merge in */
){
#define fts5PrefixMergerNextPosition(p) \
 sqlite3Fts5PoslistNext64((p)->aPos,(p)->iter.nPoslist,&(p)->iOff,&(p)->iPos)
#define FTS5_MERGE_NLIST 16
 PrefixMerger aMerger[FTS5_MERGE_NLIST];
 PrefixMerger *pHead = 0;
 int i;
 int nOut = 0;
 Fts5Buffer out = {0, 0, 0};
 Fts5Buffer tmp = {0, 0, 0};
 i64 iLastRowid = 0;

 /* Initialize a doclist-iterator for each input buffer. Arrange them in
 ** a linked-list starting at pHead in ascending order of rowid. Avoid
 ** linking any iterators already at EOF into the linked list at all. */
 assert( nBuf+1<=(int)(sizeof(aMerger)/sizeof(aMerger[0])) );
 memset(aMerger, 0, sizeof(PrefixMerger)*(nBuf+1));
 pHead = &aMerger[nBuf];
 fts5DoclistIterInit(p1, &pHead->iter);
 for(i=0; i<nBuf; i++){
 fts5DoclistIterInit(&aBuf[i], &aMerger[i].iter);
 fts5PrefixMergerInsertByRowid(&pHead, &aMerger[i]);
 nOut += aBuf[i].n;
 }
 if( nOut==0 ) return;
 nOut += p1->n + 9 + 10*nBuf;

 /* The maximum size of the output is equal to the sum of the
 ** input sizes + 1 varint (9 bytes). The extra varint is because if the
 ** first rowid in one input is a large negative number, and the first in
 ** the other a non-negative number, the delta for the non-negative
 ** number will be larger on disk than the literal integer value
 ** was.
 **
 ** Or, if the input position-lists are corrupt, then the output might
 ** include up to (nBuf+1) extra 10-byte positions created by interpreting -1
 ** (the value PoslistNext64() uses for EOF) as a position and appending
 ** it to the output. This can happen at most once for each input
 ** position-list, hence (nBuf+1) 10 byte paddings. */
 if( sqlite3Fts5BufferSize(&p->rc, &out, nOut) ) return;

 while( pHead ){
 fts5MergeAppendDocid(&out, iLastRowid, pHead->iter.iRowid);

 if( pHead->pNext && iLastRowid==pHead->pNext->iter.iRowid ){
 /* Merge data from two or more poslists */
 i64 iPrev = 0;
 int nTmp = FTS5_DATA_ZERO_PADDING;
 int nMerge = 0;
 PrefixMerger *pSave = pHead;
 PrefixMerger *pThis = 0;
 int nTail = 0;

 pHead = 0;
 while( pSave && pSave->iter.iRowid==iLastRowid ){
 PrefixMerger *pNext = pSave->pNext;
 pSave->iOff = 0;
 pSave->iPos = 0;
 pSave->aPos = &pSave->iter.aPoslist[pSave->iter.nSize];
 fts5PrefixMergerNextPosition(pSave);
 nTmp += pSave->iter.nPoslist + 10;
 nMerge++;
 fts5PrefixMergerInsertByPosition(&pHead, pSave);
 pSave = pNext;
 }

 if( pHead==0 || pHead->pNext==0 ){
 p->rc = FTS5_CORRUPT;
 break;
 }

 /* See the earlier comment in this function for an explanation of why
 ** corrupt input position lists might cause the output to consume
 ** at most nMerge*10 bytes of unexpected space. */
 if( sqlite3Fts5BufferSize(&p->rc, &tmp, nTmp+nMerge*10) ){
 break;
 }
 fts5BufferZero(&tmp);

 pThis = pHead;
 pHead = pThis->pNext;
 sqlite3Fts5PoslistSafeAppend(&tmp, &iPrev, pThis->iPos);
 fts5PrefixMergerNextPosition(pThis);
 fts5PrefixMergerInsertByPosition(&pHead, pThis);

 while( pHead->pNext ){
 pThis = pHead;
 if( pThis->iPos!=iPrev ){
 sqlite3Fts5PoslistSafeAppend(&tmp, &iPrev, pThis->iPos);
 }
 fts5PrefixMergerNextPosition(pThis);
 pHead = pThis->pNext;
 fts5PrefixMergerInsertByPosition(&pHead, pThis);
 }

 if( pHead->iPos!=iPrev ){
 sqlite3Fts5PoslistSafeAppend(&tmp, &iPrev, pHead->iPos);
 }
 nTail = pHead->iter.nPoslist - pHead->iOff;

 /* WRITEPOSLISTSIZE */
 assert_nc( tmp.n+nTail<=nTmp );
 assert( tmp.n+nTail<=nTmp+nMerge*10 );
 if( tmp.n+nTail>nTmp-FTS5_DATA_ZERO_PADDING ){
 if( p->rc==SQLITE_OK ) p->rc = FTS5_CORRUPT;
 break;
 }
 fts5BufferSafeAppendVarint(&out, (tmp.n+nTail) * 2);
 fts5BufferSafeAppendBlob(&out, tmp.p, tmp.n);
 if( nTail>0 ){
 fts5BufferSafeAppendBlob(&out, &pHead->aPos[pHead->iOff], nTail);
 }

 pHead = pSave;
 for(i=0; i<nBuf+1; i++){
 PrefixMerger *pX = &aMerger[i];
 if( pX->iter.aPoslist && pX->iter.iRowid==iLastRowid ){
 fts5DoclistIterNext(&pX->iter);
 fts5PrefixMergerInsertByRowid(&pHead, pX);
 }
 }

 }else{
 /* Copy poslist from pHead to output */
 PrefixMerger *pThis = pHead;
 Fts5DoclistIter *pI = &pThis->iter;
 fts5BufferSafeAppendBlob(&out, pI->aPoslist, pI->nPoslist+pI->nSize);
 fts5DoclistIterNext(pI);
 pHead = pThis->pNext;
 fts5PrefixMergerInsertByRowid(&pHead, pThis);
 }
 }

 fts5BufferFree(p1);
 fts5BufferFree(&tmp);
 memset(&out.p[out.n], 0, FTS5_DATA_ZERO_PADDING);
 *p1 = out;
}

static void fts5SetupPrefixIter(
 Fts5Index *p, /* Index to read from */
 int bDesc, /* True for "ORDER BY rowid DESC" */
 int iIdx, /* Index to scan for data */
 u8 *pToken, /* Buffer containing prefix to match */
 int nToken, /* Size of buffer pToken in bytes */
 Fts5Colset *pColset, /* Restrict matches to these columns */
 Fts5Iter **ppIter /* OUT: New iterator */
){
 Fts5Structure *pStruct;
 Fts5Buffer *aBuf;
 int nBuf = 32;
 int nMerge = 1;

 void (*xMerge)(Fts5Index*, Fts5Buffer*, int, Fts5Buffer*);
 void (*xAppend)(Fts5Index*, u64, Fts5Iter*, Fts5Buffer*);
 if( p->pConfig->eDetail==FTS5_DETAIL_NONE ){
 xMerge = fts5MergeRowidLists;
 xAppend = fts5AppendRowid;
 }else{
 nMerge = FTS5_MERGE_NLIST-1;
 nBuf = nMerge*8; /* Sufficient to merge (16^8)==(2^32) lists */
 xMerge = fts5MergePrefixLists;
 xAppend = fts5AppendPoslist;
 }

 aBuf = (Fts5Buffer*)fts5IdxMalloc(p, sizeof(Fts5Buffer)*nBuf);
 pStruct = fts5StructureRead(p);
 assert( p->rc!=SQLITE_OK || (aBuf && pStruct) );

 if( p->rc==SQLITE_OK ){
 const int flags = FTS5INDEX_QUERY_SCAN
 | FTS5INDEX_QUERY_SKIPEMPTY
 | FTS5INDEX_QUERY_NOOUTPUT;
 int i;
 i64 iLastRowid = 0;
 Fts5Iter *p1 = 0; /* Iterator used to gather data from index */
 Fts5Data *pData;
 Fts5Buffer doclist;
 int bNewTerm = 1;

 memset(&doclist, 0, sizeof(doclist));

 /* If iIdx is non-zero, then it is the number of a prefix-index for
 ** prefixes 1 character longer than the prefix being queried for. That
 ** index contains all the doclists required, except for the one
 ** corresponding to the prefix itself. That one is extracted from the
 ** main term index here. */
 if( iIdx!=0 ){
 int dummy = 0;
 const int f2 = FTS5INDEX_QUERY_SKIPEMPTY|FTS5INDEX_QUERY_NOOUTPUT;
 pToken[0] = FTS5_MAIN_PREFIX;
 fts5MultiIterNew(p, pStruct, f2, pColset, pToken, nToken, -1, 0, &p1);
 fts5IterSetOutputCb(&p->rc, p1);
 for(;
 fts5MultiIterEof(p, p1)==0;
 fts5MultiIterNext2(p, p1, &dummy)
 ){
 Fts5SegIter *pSeg = &p1->aSeg[ p1->aFirst[1].iFirst ];
 p1->xSetOutputs(p1, pSeg);
 if( p1->base.nData ){
 xAppend(p, (u64)p1->base.iRowid-(u64)iLastRowid, p1, &doclist);
 iLastRowid = p1->base.iRowid;
 }
 }
 fts5MultiIterFree(p1);
 }

 pToken[0] = FTS5_MAIN_PREFIX + iIdx;
 fts5MultiIterNew(p, pStruct, flags, pColset, pToken, nToken, -1, 0, &p1);
 fts5IterSetOutputCb(&p->rc, p1);

 for( /* no-op */ ;
 fts5MultiIterEof(p, p1)==0;
 fts5MultiIterNext2(p, p1, &bNewTerm)
 ){
 Fts5SegIter *pSeg = &p1->aSeg[ p1->aFirst[1].iFirst ];
 int nTerm = pSeg->term.n;
 const u8 *pTerm = pSeg->term.p;
 p1->xSetOutputs(p1, pSeg);

 assert_nc( memcmp(pToken, pTerm, MIN(nToken, nTerm))<=0 );
 if( bNewTerm ){
 if( nTerm<nToken || memcmp(pToken, pTerm, nToken) ) break;
 }

 if( p1->base.nData==0 ) continue;
 if( p1->base.iRowid<=iLastRowid && doclist.n>0 ){
 for(i=0; p->rc==SQLITE_OK && doclist.n; i++){
 int i1 = i*nMerge;
 int iStore;
 assert( i1+nMerge<=nBuf );
 for(iStore=i1; iStore<i1+nMerge; iStore++){
 if( aBuf[iStore].n==0 ){
 fts5BufferSwap(&doclist, &aBuf[iStore]);
 fts5BufferZero(&doclist);
 break;
 }
 }
 if( iStore==i1+nMerge ){
 xMerge(p, &doclist, nMerge, &aBuf[i1]);
 for(iStore=i1; iStore<i1+nMerge; iStore++){
 fts5BufferZero(&aBuf[iStore]);
 }
 }
 }
 iLastRowid = 0;
 }

 xAppend(p, (u64)p1->base.iRowid-(u64)iLastRowid, p1, &doclist);
 iLastRowid = p1->base.iRowid;
 }

 assert( (nBuf%nMerge)==0 );
 for(i=0; i<nBuf; i+=nMerge){
 int iFree;
 if( p->rc==SQLITE_OK ){
 xMerge(p, &doclist, nMerge, &aBuf[i]);
 }
 for(iFree=i; iFree<i+nMerge; iFree++){
 fts5BufferFree(&aBuf[iFree]);
 }
 }
 fts5MultiIterFree(p1);

 pData = fts5IdxMalloc(p, sizeof(*pData)+doclist.n+FTS5_DATA_ZERO_PADDING);
 if( pData ){
 pData->p = (u8*)&pData[1];
 pData->nn = pData->szLeaf = doclist.n;
 if( doclist.n ) memcpy(pData->p, doclist.p, doclist.n);
 fts5MultiIterNew2(p, pData, bDesc, ppIter);
 }
 fts5BufferFree(&doclist);
 }

 fts5StructureRelease(pStruct);
 sqlite3_free(aBuf);
}

/*
** Indicate that all subsequent calls to sqlite3Fts5IndexWrite() pertain
** to the document with rowid iRowid.
*/
static int sqlite3Fts5IndexBeginWrite(Fts5Index *p, int bDelete, i64 iRowid){
 assert( p->rc==SQLITE_OK );

 /* Allocate the hash table if it has not already been allocated */
 if( p->pHash==0 ){
 p->rc = sqlite3Fts5HashNew(p->pConfig, &p->pHash, &p->nPendingData);
 }

 /* Flush the hash table to disk if required */
 if( iRowid<p->iWriteRowid
 || (iRowid==p->iWriteRowid && p->bDelete==0)
 || (p->nPendingData > p->pConfig->nHashSize)
 ){
 fts5IndexFlush(p);
 }

 p->iWriteRowid = iRowid;
 p->bDelete = bDelete;
 if( bDelete==0 ){
 p->nPendingRow++;
 }
 return fts5IndexReturn(p);
}

/*
** Commit data to disk.
*/
static int sqlite3Fts5IndexSync(Fts5Index *p){
 assert( p->rc==SQLITE_OK );
 fts5IndexFlush(p);
 sqlite3Fts5IndexCloseReader(p);
 return fts5IndexReturn(p);
}

/*
** Discard any data stored in the in-memory hash tables. Do not write it
** to the database. Additionally, assume that the contents of the %_data
** table may have changed on disk. So any in-memory caches of %_data
** records must be invalidated.
*/
static int sqlite3Fts5IndexRollback(Fts5Index *p){
 sqlite3Fts5IndexCloseReader(p);
 fts5IndexDiscardData(p);
 fts5StructureInvalidate(p);
 /* assert( p->rc==SQLITE_OK ); */
 return SQLITE_OK;
}

/*
** The %_data table is completely empty when this function is called. This
** function populates it with the initial structure objects for each index,
** and the initial version of the "averages" record (a zero-byte blob).
*/
static int sqlite3Fts5IndexReinit(Fts5Index *p){
 Fts5Structure s;
 fts5StructureInvalidate(p);
 fts5IndexDiscardData(p);
 memset(&s, 0, sizeof(Fts5Structure));
 if( p->pConfig->bContentlessDelete ){
 s.nOriginCntr = 1;
 }
 fts5DataWrite(p, FTS5_AVERAGES_ROWID, (const u8*)"", 0);
 fts5StructureWrite(p, &s);
 return fts5IndexReturn(p);
}

/*
** Open a new Fts5Index handle. If the bCreate argument is true, create
** and initialize the underlying %_data table.
**
** If successful, set *pp to point to the new object and return SQLITE_OK.
** Otherwise, set *pp to NULL and return an SQLite error code.
*/
static int sqlite3Fts5IndexOpen(
 Fts5Config *pConfig,
 int bCreate,
 Fts5Index **pp,
 char **pzErr
){
 int rc = SQLITE_OK;
 Fts5Index *p; /* New object */

 *pp = p = (Fts5Index*)sqlite3Fts5MallocZero(&rc, sizeof(Fts5Index));
 if( rc==SQLITE_OK ){
 p->pConfig = pConfig;
 p->nWorkUnit = FTS5_WORK_UNIT;
 p->zDataTbl = sqlite3Fts5Mprintf(&rc, "%s_data", pConfig->zName);
 if( p->zDataTbl && bCreate ){
 rc = sqlite3Fts5CreateTable(
 pConfig, "data", "id INTEGER PRIMARY KEY, block BLOB", 0, pzErr
 );
 if( rc==SQLITE_OK ){
 rc = sqlite3Fts5CreateTable(pConfig, "idx",
 "segid, term, pgno, PRIMARY KEY(segid, term)",
 1, pzErr
 );
 }
 if( rc==SQLITE_OK ){
 rc = sqlite3Fts5IndexReinit(p);
 }
 }
 }

 assert( rc!=SQLITE_OK || p->rc==SQLITE_OK );
 if( rc ){
 sqlite3Fts5IndexClose(p);
 *pp = 0;
 }
 return rc;
}

/*
** Close a handle opened by an earlier call to sqlite3Fts5IndexOpen().
*/
static int sqlite3Fts5IndexClose(Fts5Index *p){
 int rc = SQLITE_OK;
 if( p ){
 assert( p->pReader==0 );
 fts5StructureInvalidate(p);
 sqlite3_finalize(p->pWriter);
 sqlite3_finalize(p->pDeleter);
 sqlite3_finalize(p->pIdxWriter);
 sqlite3_finalize(p->pIdxDeleter);
 sqlite3_finalize(p->pIdxSelect);
 sqlite3_finalize(p->pIdxNextSelect);
 sqlite3_finalize(p->pDataVersion);
 sqlite3_finalize(p->pDeleteFromIdx);
 sqlite3Fts5HashFree(p->pHash);
 sqlite3_free(p->zDataTbl);
 sqlite3_free(p);
 }
 return rc;
}

/*
** Argument p points to a buffer containing utf-8 text that is n bytes in
** size. Return the number of bytes in the nChar character prefix of the
** buffer, or 0 if there are less than nChar characters in total.
*/
static int sqlite3Fts5IndexCharlenToBytelen(
 const char *p,
 int nByte,
 int nChar
){
 int n = 0;
 int i;
 for(i=0; i<nChar; i++){
 if( n>=nByte ) return 0; /* Input contains fewer than nChar chars */
 if( (unsigned char)p[n++]>=0xc0 ){
 if( n>=nByte ) return 0;
 while( (p[n] & 0xc0)==0x80 ){
 n++;
 if( n>=nByte ){
 if( i+1==nChar ) break;
 return 0;
 }
 }
 }
 }
 return n;
}

/*
** pIn is a UTF-8 encoded string, nIn bytes in size. Return the number of
** unicode characters in the string.
*/
static int fts5IndexCharlen(const char *pIn, int nIn){
 int nChar = 0;
 int i = 0;
 while( i<nIn ){
 if( (unsigned char)pIn[i++]>=0xc0 ){
 while( i<nIn && (pIn[i] & 0xc0)==0x80 ) i++;
 }
 nChar++;
 }
 return nChar;
}

/*
** Insert or remove data to or from the index. Each time a document is
** added to or removed from the index, this function is called one or more
** times.
**
** For an insert, it must be called once for each token in the new document.
** If the operation is a delete, it must be called (at least) once for each
** unique token in the document with an iCol value less than zero. The iPos
** argument is ignored for a delete.
*/
static int sqlite3Fts5IndexWrite(
 Fts5Index *p, /* Index to write to */
 int iCol, /* Column token appears in (-ve -> delete) */
 int iPos, /* Position of token within column */
 const char *pToken, int nToken /* Token to add or remove to or from index */
){
 int i; /* Used to iterate through indexes */
 int rc = SQLITE_OK; /* Return code */
 Fts5Config *pConfig = p->pConfig;

 assert( p->rc==SQLITE_OK );
 assert( (iCol<0)==p->bDelete );

 /* Add the entry to the main terms index. */
 rc = sqlite3Fts5HashWrite(
 p->pHash, p->iWriteRowid, iCol, iPos, FTS5_MAIN_PREFIX, pToken, nToken
 );

 for(i=0; i<pConfig->nPrefix && rc==SQLITE_OK; i++){
 const int nChar = pConfig->aPrefix[i];
 int nByte = sqlite3Fts5IndexCharlenToBytelen(pToken, nToken, nChar);
 if( nByte ){
 rc = sqlite3Fts5HashWrite(p->pHash,
 p->iWriteRowid, iCol, iPos, (char)(FTS5_MAIN_PREFIX+i+1), pToken,
 nByte
 );
 }
 }

 return rc;
}

/*
** pToken points to a buffer of size nToken bytes containing a search
** term, including the index number at the start, used on a tokendata=1
** table. This function returns true if the term in buffer pBuf matches
** token pToken/nToken.
*/
static int fts5IsTokendataPrefix(
 Fts5Buffer *pBuf,
 const u8 *pToken,
 int nToken
){
 return (
 pBuf->n>=nToken
 && 0==memcmp(pBuf->p, pToken, nToken)
 && (pBuf->n==nToken || pBuf->p[nToken]==0x00)
 );
}

/*
** Ensure the segment-iterator passed as the only argument points to EOF.
*/
static void fts5SegIterSetEOF(Fts5SegIter *pSeg){
 fts5DataRelease(pSeg->pLeaf);
 pSeg->pLeaf = 0;
}

/*
** Usually, a tokendata=1 iterator (struct Fts5TokenDataIter) accumulates an
** array of these for each row it visits. Or, for an iterator used by an
** "ORDER BY rank" query, it accumulates an array of these for the entire
** query.
**
** Each instance in the array indicates the iterator (and therefore term)
** associated with position iPos of rowid iRowid. This is used by the
** xInstToken() API.
*/
struct Fts5TokenDataMap {
 i64 iRowid; /* Row this token is located in */
 i64 iPos; /* Position of token */
 int iIter; /* Iterator token was read from */
};

/*
** An object used to supplement Fts5Iter for tokendata=1 iterators.
*/
struct Fts5TokenDataIter {
 int nIter;
 int nIterAlloc;

 int nMap;
 int nMapAlloc;
 Fts5TokenDataMap *aMap;

 Fts5PoslistReader *aPoslistReader;
 int *aPoslistToIter;
 Fts5Iter *apIter[1];
};

/*
** This function appends iterator pAppend to Fts5TokenDataIter pIn and
** returns the result.
*/
static Fts5TokenDataIter *fts5AppendTokendataIter(
 Fts5Index *p, /* Index object (for error code) */
 Fts5TokenDataIter *pIn, /* Current Fts5TokenDataIter struct */
 Fts5Iter *pAppend /* Append this iterator */
){
 Fts5TokenDataIter *pRet = pIn;

 if( p->rc==SQLITE_OK ){
 if( pIn==0 || pIn->nIter==pIn->nIterAlloc ){
 int nAlloc = pIn ? pIn->nIterAlloc*2 : 16;
 int nByte = nAlloc * sizeof(Fts5Iter*) + sizeof(Fts5TokenDataIter);
 Fts5TokenDataIter *pNew = (Fts5TokenDataIter*)sqlite3_realloc(pIn, nByte);

 if( pNew==0 ){
 p->rc = SQLITE_NOMEM;
 }else{
 if( pIn==0 ) memset(pNew, 0, nByte);
 pRet = pNew;
 pNew->nIterAlloc = nAlloc;
 }
 }
 }
 if( p->rc ){
 sqlite3Fts5IterClose((Fts5IndexIter*)pAppend);
 }else{
 pRet->apIter[pRet->nIter++] = pAppend;
 }
 assert( pRet==0 || pRet->nIter<=pRet->nIterAlloc );

 return pRet;
}

/*
** Delete an Fts5TokenDataIter structure and its contents.
*/
static void fts5TokendataIterDelete(Fts5TokenDataIter *pSet){
 if( pSet ){
 int ii;
 for(ii=0; ii<pSet->nIter; ii++){
 fts5MultiIterFree(pSet->apIter[ii]);
 }
 sqlite3_free(pSet->aPoslistReader);
 sqlite3_free(pSet->aMap);
 sqlite3_free(pSet);
 }
}

/*
** Append a mapping to the token-map belonging to object pT.
*/
static void fts5TokendataIterAppendMap(
 Fts5Index *p,
 Fts5TokenDataIter *pT,
 int iIter,
 i64 iRowid,
 i64 iPos
){
 if( p->rc==SQLITE_OK ){
 if( pT->nMap==pT->nMapAlloc ){
 int nNew = pT->nMapAlloc ? pT->nMapAlloc*2 : 64;
 int nByte = nNew * sizeof(Fts5TokenDataMap);
 Fts5TokenDataMap *aNew;

 aNew = (Fts5TokenDataMap*)sqlite3_realloc(pT->aMap, nByte);
 if( aNew==0 ){
 p->rc = SQLITE_NOMEM;
 return;
 }

 pT->aMap = aNew;
 pT->nMapAlloc = nNew;
 }

 pT->aMap[pT->nMap].iRowid = iRowid;
 pT->aMap[pT->nMap].iPos = iPos;
 pT->aMap[pT->nMap].iIter = iIter;
 pT->nMap++;
 }
}

/*
** The iterator passed as the only argument must be a tokendata=1 iterator
** (pIter->pTokenDataIter!=0). This function sets the iterator output
** variables (pIter->base.*) according to the contents of the current
** row.
*/
static void fts5IterSetOutputsTokendata(Fts5Iter *pIter){
 int ii;
 int nHit = 0;
 i64 iRowid = SMALLEST_INT64;
 int iMin = 0;

 Fts5TokenDataIter *pT = pIter->pTokenDataIter;

 pIter->base.nData = 0;
 pIter->base.pData = 0;

 for(ii=0; ii<pT->nIter; ii++){
 Fts5Iter *p = pT->apIter[ii];
 if( p->base.bEof==0 ){
 if( nHit==0 || p->base.iRowid<iRowid ){
 iRowid = p->base.iRowid;
 nHit = 1;
 pIter->base.pData = p->base.pData;
 pIter->base.nData = p->base.nData;
 iMin = ii;
 }else if( p->base.iRowid==iRowid ){
 nHit++;
 }
 }
 }

 if( nHit==0 ){
 pIter->base.bEof = 1;
 }else{
 int eDetail = pIter->pIndex->pConfig->eDetail;
 pIter->base.bEof = 0;
 pIter->base.iRowid = iRowid;

 if( nHit==1 && eDetail==FTS5_DETAIL_FULL ){
 fts5TokendataIterAppendMap(pIter->pIndex, pT, iMin, iRowid, -1);
 }else
 if( nHit>1 && eDetail!=FTS5_DETAIL_NONE ){
 int nReader = 0;
 int nByte = 0;
 i64 iPrev = 0;

 /* Allocate array of iterators if they are not already allocated. */
 if( pT->aPoslistReader==0 ){
 pT->aPoslistReader = (Fts5PoslistReader*)sqlite3Fts5MallocZero(
 &pIter->pIndex->rc,
 pT->nIter * (sizeof(Fts5PoslistReader) + sizeof(int))
 );
 if( pT->aPoslistReader==0 ) return;
 pT->aPoslistToIter = (int*)&pT->aPoslistReader[pT->nIter];
 }

 /* Populate an iterator for each poslist that will be merged */
 for(ii=0; ii<pT->nIter; ii++){
 Fts5Iter *p = pT->apIter[ii];
 if( iRowid==p->base.iRowid ){
 pT->aPoslistToIter[nReader] = ii;
 sqlite3Fts5PoslistReaderInit(
 p->base.pData, p->base.nData, &pT->aPoslistReader[nReader++]
 );
 nByte += p->base.nData;
 }
 }

 /* Ensure the output buffer is large enough */
 if( fts5BufferGrow(&pIter->pIndex->rc, &pIter->poslist, nByte+nHit*10) ){
 return;
 }

 /* Ensure the token-mapping is large enough */
 if( eDetail==FTS5_DETAIL_FULL && pT->nMapAlloc<(pT->nMap + nByte) ){
 int nNew = (pT->nMapAlloc + nByte) * 2;
 Fts5TokenDataMap *aNew = (Fts5TokenDataMap*)sqlite3_realloc(
 pT->aMap, nNew*sizeof(Fts5TokenDataMap)
 );
 if( aNew==0 ){
 pIter->pIndex->rc = SQLITE_NOMEM;
 return;
 }
 pT->aMap = aNew;
 pT->nMapAlloc = nNew;
 }

 pIter->poslist.n = 0;

 while( 1 ){
 i64 iMinPos = LARGEST_INT64;

 /* Find smallest position */
 iMin = 0;
 for(ii=0; ii<nReader; ii++){
 Fts5PoslistReader *pReader = &pT->aPoslistReader[ii];
 if( pReader->bEof==0 ){
 if( pReader->iPos<iMinPos ){
 iMinPos = pReader->iPos;
 iMin = ii;
 }
 }
 }

 /* If all readers were at EOF, break out of the loop. */
 if( iMinPos==LARGEST_INT64 ) break;

 sqlite3Fts5PoslistSafeAppend(&pIter->poslist, &iPrev, iMinPos);
 sqlite3Fts5PoslistReaderNext(&pT->aPoslistReader[iMin]);

 if( eDetail==FTS5_DETAIL_FULL ){
 pT->aMap[pT->nMap].iPos = iMinPos;
 pT->aMap[pT->nMap].iIter = pT->aPoslistToIter[iMin];
 pT->aMap[pT->nMap].iRowid = iRowid;
 pT->nMap++;
 }
 }

 pIter->base.pData = pIter->poslist.p;
 pIter->base.nData = pIter->poslist.n;
 }
 }
}

/*
** The iterator passed as the only argument must be a tokendata=1 iterator
** (pIter->pTokenDataIter!=0). This function advances the iterator. If
** argument bFrom is false, then the iterator is advanced to the next
** entry. Or, if bFrom is true, it is advanced to the first entry with
** a rowid of iFrom or greater.
*/
static void fts5TokendataIterNext(Fts5Iter *pIter, int bFrom, i64 iFrom){
 int ii;
 Fts5TokenDataIter *pT = pIter->pTokenDataIter;
 Fts5Index *pIndex = pIter->pIndex;

 for(ii=0; ii<pT->nIter; ii++){
 Fts5Iter *p = pT->apIter[ii];
 if( p->base.bEof==0
 && (p->base.iRowid==pIter->base.iRowid || (bFrom && p->base.iRowid<iFrom))
 ){
 fts5MultiIterNext(pIndex, p, bFrom, iFrom);
 while( bFrom && p->base.bEof==0
 && p->base.iRowid<iFrom
 && pIndex->rc==SQLITE_OK
 ){
 fts5MultiIterNext(pIndex, p, 0, 0);
 }
 }
 }

 if( pIndex->rc==SQLITE_OK ){
 fts5IterSetOutputsTokendata(pIter);
 }
}

/*
** If the segment-iterator passed as the first argument is at EOF, then
** set pIter->term to a copy of buffer pTerm.
*/
static void fts5TokendataSetTermIfEof(Fts5Iter *pIter, Fts5Buffer *pTerm){
 if( pIter && pIter->aSeg[0].pLeaf==0 ){
 fts5BufferSet(&pIter->pIndex->rc, &pIter->aSeg[0].term, pTerm->n, pTerm->p);
 }
}

/*
** This function sets up an iterator to use for a non-prefix query on a
** tokendata=1 table.
*/
static Fts5Iter *fts5SetupTokendataIter(
 Fts5Index *p, /* FTS index to query */
 const u8 *pToken, /* Buffer containing query term */
 int nToken, /* Size of buffer pToken in bytes */
 Fts5Colset *pColset /* Colset to filter on */
){
 Fts5Iter *pRet = 0;
 Fts5TokenDataIter *pSet = 0;
 Fts5Structure *pStruct = 0;
 const int flags = FTS5INDEX_QUERY_SCANONETERM | FTS5INDEX_QUERY_SCAN;

 Fts5Buffer bSeek = {0, 0, 0};
 Fts5Buffer *pSmall = 0;

 fts5IndexFlush(p);
 pStruct = fts5StructureRead(p);

 while( p->rc==SQLITE_OK ){
 Fts5Iter *pPrev = pSet ? pSet->apIter[pSet->nIter-1] : 0;
 Fts5Iter *pNew = 0;
 Fts5SegIter *pNewIter = 0;
 Fts5SegIter *pPrevIter = 0;

 int iLvl, iSeg, ii;

 pNew = fts5MultiIterAlloc(p, pStruct->nSegment);
 if( pSmall ){
 fts5BufferSet(&p->rc, &bSeek, pSmall->n, pSmall->p);
 fts5BufferAppendBlob(&p->rc, &bSeek, 1, (const u8*)"\0");
 }else{
 fts5BufferSet(&p->rc, &bSeek, nToken, pToken);
 }
 if( p->rc ){
 sqlite3Fts5IterClose((Fts5IndexIter*)pNew);
 break;
 }

 pNewIter = &pNew->aSeg[0];
 pPrevIter = (pPrev ? &pPrev->aSeg[0] : 0);
 for(iLvl=0; iLvl<pStruct->nLevel; iLvl++){
 for(iSeg=pStruct->aLevel[iLvl].nSeg-1; iSeg>=0; iSeg--){
 Fts5StructureSegment *pSeg = &pStruct->aLevel[iLvl].aSeg[iSeg];
 int bDone = 0;

 if( pPrevIter ){
 if( fts5BufferCompare(pSmall, &pPrevIter->term) ){
 memcpy(pNewIter, pPrevIter, sizeof(Fts5SegIter));
 memset(pPrevIter, 0, sizeof(Fts5SegIter));
 bDone = 1;
 }else if( pPrevIter->iEndofDoclist>pPrevIter->pLeaf->szLeaf ){
 fts5SegIterNextInit(p,(const char*)bSeek.p,bSeek.n-1,pSeg,pNewIter);
 bDone = 1;
 }
 }

 if( bDone==0 ){
 fts5SegIterSeekInit(p, bSeek.p, bSeek.n, flags, pSeg, pNewIter);
 }

 if( pPrevIter ){
 if( pPrevIter->pTombArray ){
 pNewIter->pTombArray = pPrevIter->pTombArray;
 pNewIter->pTombArray->nRef++;
 }
 }else{
 fts5SegIterAllocTombstone(p, pNewIter);
 }

 pNewIter++;
 if( pPrevIter ) pPrevIter++;
 if( p->rc ) break;
 }
 }
 fts5TokendataSetTermIfEof(pPrev, pSmall);

 pNew->bSkipEmpty = 1;
 pNew->pColset = pColset;
 fts5IterSetOutputCb(&p->rc, pNew);

 /* Loop through all segments in the new iterator. Find the smallest
 ** term that any segment-iterator points to. Iterator pNew will be
 ** used for this term. Also, set any iterator that points to a term that
 ** does not match pToken/nToken to point to EOF */
 pSmall = 0;
 for(ii=0; ii<pNew->nSeg; ii++){
 Fts5SegIter *pII = &pNew->aSeg[ii];
 if( 0==fts5IsTokendataPrefix(&pII->term, pToken, nToken) ){
 fts5SegIterSetEOF(pII);
 }
--> --------------------

--> maximum size reached

--> --------------------

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