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When a relation has been proven empty by constraint exclusion, propagate that

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knowledge up through any joins it participates in.  We were doing that already
in some special cases but not in the general case.  Also, defend against zero
row estimates for the input relations in cost_mergejoin --- this fix may have
eliminated the only scenario in which that can happen, but be safe.  Per
report from Alex Solovey.
This commit is contained in:
Tom Lane
2008-03-24 21:53:04 +00:00
parent 2a346725ba
commit fd791e7b5a
5 changed files with 113 additions and 11 deletions
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8
src/backend/optimizer/path/costsize.c
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@@ -54,7 +54,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.191 2008/01/01 19:45:50 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.192 2008/03/24 21:53:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1385,6 +1385,12 @@ cost_mergejoin(MergePath *path, PlannerInfo *root)
Selectivity joininfactor;
Path sort_path; /* dummy for result of cost_sort */
/* Protect some assumptions below that rowcounts aren't zero */
if (outer_path_rows <= 0)
outer_path_rows = 1;
if (inner_path_rows <= 0)
inner_path_rows = 1;
if (!enable_mergejoin)
startup_cost += disable_cost;