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Allow GIN's extractQuery method to signal that nothing can satisfy the query.

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In this case extractQuery should returns -1 as nentries. This changes
prototype of extractQuery method to use int32* instead of uint32* for
nentries argument.
Based on that gincostestimate may see two corner cases: nothing will be found
or seqscan should be used.

Per proposal at http://archives.postgresql.org/pgsql-hackers/2007-01/msg01581.php

PS tsearch_core patch should be sightly modified to support changes, but I'm
waiting a verdict about reviewing of tsearch_core patch.
This commit is contained in:
Teodor Sigaev
2007-01-31 15:09:45 +00:00
parent 147a3ce149
commit d4c6da1527
11 changed files with 199 additions and 29 deletions
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19
src/backend/access/gin/ginarrayproc.c
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@@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/gin/ginarrayproc.c,v 1.8 2007/01/05 22:19:21 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/gin/ginarrayproc.c,v 1.9 2007/01/31 15:09:45 teodor Exp $
*-------------------------------------------------------------------------
*/
#include "postgres.h"
@@ -38,7 +38,7 @@ Datum
ginarrayextract(PG_FUNCTION_ARGS)
{
ArrayType *array;
uint32 *nentries = (uint32 *) PG_GETARG_POINTER(1);
int32 *nentries = (int32 *) PG_GETARG_POINTER(1);
Datum *entries = NULL;
int16 elmlen;
bool elmbyval;
@@ -60,6 +60,21 @@ ginarrayextract(PG_FUNCTION_ARGS)
elmlen, elmbyval, elmalign,
&entries, NULL, (int *) nentries);
if ( *nentries == 0 && PG_NARGS() == 3 )
{
switch( PG_GETARG_UINT16(2) )
{
case GinOverlapStrategy:
*nentries = -1; /* nobody can be found */
break;
case GinContainsStrategy:
case GinContainedStrategy:
case GinEqualStrategy:
default: /* require fullscan: GIN can't find void arrays */
break;
}
}
/* we should not free array, entries[i] points into it */
PG_RETURN_POINTER(entries);
}