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Teach the planner to treat a partial unique index as proving a variable is

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unique for a particular query, if the index predicate is satisfied.  This
requires a bit of reordering of operations so that we check the predicates
before doing any selectivity estimates, but shouldn't really cause any
noticeable slowdown.  Per a comment from Michal Politowski.
This commit is contained in:
Tom Lane
2009-02-15 20:16:21 +00:00
parent 57b5984d24
commit ce6e31de9c
5 changed files with 70 additions and 39 deletions
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13
src/backend/optimizer/path/indxpath.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.235 2009/01/01 17:23:43 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.236 2009/02/15 20:16:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1367,8 +1367,12 @@ match_rowcompare_to_indexcol(IndexOptInfo *index,
/*
* check_partial_indexes
* Check each partial index of the relation, and mark it predOK or not
* depending on whether the predicate is satisfied for this query.
* Check each partial index of the relation, and mark it predOK if
* the index's predicate is satisfied for this query.
*
* Note: it is possible for this to get re-run after adding more restrictions
* to the rel; so we might be able to prove more indexes OK. We assume that
* adding more restrictions can't make an index not OK.
*/
void
check_partial_indexes(PlannerInfo *root, RelOptInfo *rel)
@ -1383,6 +1387,9 @@ check_partial_indexes(PlannerInfo *root, RelOptInfo *rel)
if (index->indpred == NIL)
continue; /* ignore non-partial indexes */
if (index->predOK)
continue; /* don't repeat work if already proven OK */
index->predOK = predicate_implied_by(index->indpred,
restrictinfo_list);
}