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Commitaca467b

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Save another little bit of planner overhead on simple queries, by having
clauselist_selectivity skip some analysis that's useless when there's onlyone clause in the given list. Actually this can win even for not-so-simplequeries, because we also apply clauselist_selectivity to sublists such as thequals matching an index; which are likely to have only a single entry evenwhen the total query is quite complicated.
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‎src/backend/optimizer/path/clausesel.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -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/clausesel.c,v 1.87 2007/08/31 23:35:22 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/path/clausesel.c,v 1.88 2007/11/24 19:08:51 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -100,6 +100,14 @@ clauselist_selectivity(PlannerInfo *root,
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RangeQueryClause*rqlist=NULL;
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ListCell*l;
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/*
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* If there's exactly one clause, then no use in trying to match up
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* pairs, so just go directly to clause_selectivity().
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*/
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if (list_length(clauses)==1)
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returnclause_selectivity(root, (Node*)linitial(clauses),
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varRelid,jointype);
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/*
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* Initial scan over clauses. Anything that doesn't look like a potential
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* rangequery clause gets multiplied into s1 and forgotten. Anything that

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