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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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16
src/backend/optimizer/path/allpaths.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.179 2009/01/01 17:23:43 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.180 2009/02/15 20:16:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -225,19 +225,25 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
return;
}
/*
* Test any partial indexes of rel for applicability. We must do this
* first since partial unique indexes can affect size estimates.
*/
check_partial_indexes(root, rel);
/* Mark rel with estimated output rows, width, etc */
set_baserel_size_estimates(root, rel);
/* Test any partial indexes of rel for applicability */
check_partial_indexes(root, rel);
/*
* Check to see if we can extract any restriction conditions from join
* quals that are OR-of-AND structures. If so, add them to the rel's
* restriction list, and recompute the size estimates.
* restriction list, and redo the above steps.
*/
if (create_or_index_quals(root, rel))
{
check_partial_indexes(root, rel);
set_baserel_size_estimates(root, rel);
}
/*
* Generate paths and add them to the rel's pathlist.