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Fix brain fade in join-removal patch: a pushed-down clause in the outer join's

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restrict list is not just something to ignore, it's actually grounds to
abandon the optimization entirely.  Per bug #5255 from Matteo Beccati.
This commit is contained in:
Tom Lane 2009-12-25 17:11:32 +00:00
parent 666c845c75
commit f9845aca2b
1 changed files with 13 additions and 5 deletions
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18
src/backend/optimizer/path/joinpath.c
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@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.126 2009/09/19 17:48:09 tgl Exp $ * $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.127 2009/12/25 17:11:32 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -228,6 +228,11 @@ join_is_removable(PlannerInfo *root,
* We can't remove the join if any inner-rel attributes are used above * We can't remove the join if any inner-rel attributes are used above
* the join. * the join.
* *
* Note that this test only detects use of inner-rel attributes in
* higher join conditions and the target list. There might be such
* attributes in pushed-down conditions at this join, too. We check
* that case below.
*
* As a micro-optimization, it seems better to start with max_attr and * As a micro-optimization, it seems better to start with max_attr and
* count down rather than starting with min_attr and counting up, on the * count down rather than starting with min_attr and counting up, on the
* theory that the system attributes are somewhat less likely to be wanted * theory that the system attributes are somewhat less likely to be wanted
@ -253,13 +258,16 @@ join_is_removable(PlannerInfo *root,
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l); RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
/* /*
* We are always considering an outer join here, so ignore pushed-down * If we find a pushed-down clause, it must have come from above the
* clauses. Also ignore anything that doesn't have a mergejoinable * outer join and it must contain references to the inner rel. (If
* operator. * it had only outer-rel variables, it'd have been pushed down into
* the outer rel.) Therefore, we can conclude that join removal
* is unsafe without any examination of the clause contents.
*/ */
if (restrictinfo->is_pushed_down) if (restrictinfo->is_pushed_down)
continue; return false;
/* Ignore if it's not a mergejoinable clause */
if (!restrictinfo->can_join || if (!restrictinfo->can_join ||
restrictinfo->mergeopfamilies == NIL) restrictinfo->mergeopfamilies == NIL)
continue; /* not mergejoinable */ continue; /* not mergejoinable */