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Adjust OR indexscan logic to not generate redundant condition-free OR 

indexscans involving partial indexes.  These would always be dominated
by a simple indexscan on such an index, so there's no point in considering
them.  Fixes overoptimism in a patch I applied last October.
This commit is contained in:
Tom Lane 2005-03-01 01:40:05 +00:00
parent 295dd338c3
commit 95871703e3
1 changed files with 8 additions and 4 deletions
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12
src/backend/optimizer/path/orindxpath.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/orindxpath.c,v 1.64 2004/12/31 22:00:04 pgsql Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/orindxpath.c,v 1.65 2005/03/01 01:40:05 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -387,10 +387,14 @@ best_or_subclause_index(Query *root,
/*
* Ignore index if it doesn't match the subclause at all; except
* that if it's a partial index, consider it anyway, since the
* selectivity of the predicate alone might make the index useful.
* that if it's a partial index matching the current OR subclause,
* consider it anyway, since effectively we are using the index
* predicate to match the subclause. (Note: we exclude partial
* indexes that are predOK; else such a partial index would be
* considered to match *every* OR subclause, generating bogus OR
* plans that are redundant with the basic scan on that index.)
*/
if (indexclauses == NIL && index->indpred == NIL)
if (indexclauses == NIL && (index->indpred == NIL || index->predOK))
continue;
/* Convert clauses to indexquals the executor can handle */