Quelle  btree_gist.c

/*
 * contrib/btree_gist/btree_gist.c
 */
#include "postgres.h"

#include "access/cmptype.h"
#include "access/stratnum.h"
#include "utils/builtins.h"

PG_MODULE_MAGIC_EXT(
     .name = "btree_gist",
     .version = PG_VERSION
);

PG_FUNCTION_INFO_V1(gbt_decompress);
PG_FUNCTION_INFO_V1(gbtreekey_in);
PG_FUNCTION_INFO_V1(gbtreekey_out);
PG_FUNCTION_INFO_V1(gist_translate_cmptype_btree);

/**************************************************
 * In/Out for keys
 **************************************************/


Datum
gbtreekey_in(PG_FUNCTION_ARGS)
{
 Oid   typioparam = PG_GETARG_OID(1);

 ereport(ERROR,
   (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
    errmsg("cannot accept a value of type %s",
     format_type_extended(typioparam, -1,
           FORMAT_TYPE_ALLOW_INVALID))));

 PG_RETURN_VOID();   /* keep compiler quiet */
}

Datum
gbtreekey_out(PG_FUNCTION_ARGS)
{
 /* Sadly, we do not receive any indication of the specific type */
 ereport(ERROR,
   (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
    errmsg("cannot display a value of type %s", "gbtreekey?")));

 PG_RETURN_VOID();   /* keep compiler quiet */
}


/*
** GiST DeCompress methods
** do not do anything.
*/
Datum
gbt_decompress(PG_FUNCTION_ARGS)
{
 PG_RETURN_POINTER(PG_GETARG_POINTER(0));
}

/*
 * Returns the btree number for supported operators, otherwise invalid.
 */
Datum
gist_translate_cmptype_btree(PG_FUNCTION_ARGS)
{
 CompareType cmptype = PG_GETARG_INT32(0);

 switch (cmptype)
 {
  case COMPARE_EQ:
   PG_RETURN_UINT16(BTEqualStrategyNumber);
  case COMPARE_LT:
   PG_RETURN_UINT16(BTLessStrategyNumber);
  case COMPARE_LE:
   PG_RETURN_UINT16(BTLessEqualStrategyNumber);
  case COMPARE_GT:
   PG_RETURN_UINT16(BTGreaterStrategyNumber);
  case COMPARE_GE:
   PG_RETURN_UINT16(BTGreaterEqualStrategyNumber);
  default:
   PG_RETURN_UINT16(InvalidStrategy);
 }
}