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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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15
contrib/intarray/_int_gin.c
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@ -6,7 +6,7 @@ Datum ginint4_queryextract(PG_FUNCTION_ARGS);
Datum
ginint4_queryextract(PG_FUNCTION_ARGS)
{
uint32 *nentries = (uint32 *) PG_GETARG_POINTER(1);
int32 *nentries = (int32 *) PG_GETARG_POINTER(1);
StrategyNumber strategy = PG_GETARG_UINT16(2);
Datum *res = NULL;
@ -57,6 +57,19 @@ ginint4_queryextract(PG_FUNCTION_ARGS)
}
}
if ( nentries == 0 )
{
switch( strategy )
{
case BooleanSearchStrategy:
case RTOverlapStrategyNumber:
*nentries = -1; /* nobody can be found */
break;
default: /* require fullscan: GIN can't find void arrays */
break;
}
}
PG_RETURN_POINTER(res);
}