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Commit9587170

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Adjust OR indexscan logic to not generate redundant condition-free OR
indexscans involving partial indexes. These would always be dominatedby a simple indexscan on such an index, so there's no point in consideringthem. Fixes overoptimism in a patch I applied last October.
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‎src/backend/optimizer/path/orindxpath.c‎

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@@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/path/orindxpath.c,v 1.64 2004/12/31 22:00:04 pgsql Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/path/orindxpath.c,v 1.65 2005/03/01 01:40:05 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -387,10 +387,14 @@ best_or_subclause_index(Query *root,
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/*
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* Ignore index if it doesn't match the subclause at all; except
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* that if it's a partial index, consider it anyway, since the
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* selectivity of the predicate alone might make the index useful.
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* that if it's a partial index matching the current OR subclause,
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* consider it anyway, since effectively we are using the index
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* predicate to match the subclause. (Note: we exclude partial
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* indexes that are predOK; else such a partial index would be
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* considered to match *every* OR subclause, generating bogus OR
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* plans that are redundant with the basic scan on that index.)
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*/
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if (indexclauses==NIL&&index->indpred==NIL)
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if (indexclauses==NIL&&(index->indpred==NIL||index->predOK))
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continue;
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/* Convert clauses to indexquals the executor can handle */

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