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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2008-12-01 21:06:13 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2008-12-01 21:06:13 +0000 |
| commit | a1feb90ef32999f188f150795f896bd4ec839223 (patch) | |
| tree | ef4ef4f938da0b0dced6f1e2b207f3e2ce7953f3 /src/backend/nodes/outfuncs.c | |
| parent | 7fb27531e8f51448f061a007534db67e0467a23e (diff) | |
| download | postgresql-a1feb90ef32999f188f150795f896bd4ec839223.tar.gz | |
Fix an oversight in the code that makes transitive-equality deductions from
outer join clauses. Given, say,
... from a left join b on a.a1 = b.b1 where a.a1 = 42;
we'll deduce a clause b.b1 = 42 and then mark the original join clause
redundant (we can't remove it completely for reasons I don't feel like
squeezing into this log entry). However the original implementation of
that wasn't bulletproof, because clause_selectivity() wouldn't honor
this_selec if given nonzero varRelid --- which in practice meant that
it worked as desired *except* when considering index scan quals. Which
resulted in bogus underestimation of the size of the indexscan result for
an inner indexscan in an outer join, and consequently a possibly bad
choice of indexscan vs. bitmap scan. Fix by introducing an explicit test
into clause_selectivity(). Also, to make sure we don't trigger that test
in corner cases, change the convention to be that this_selec > 1, not
this_selec = 1, means it's been marked redundant. Per trouble report from
Scara Maccai.
Back-patch to 8.2, where the problem was introduced.
Diffstat (limited to 'src/backend/nodes/outfuncs.c')
| -rw-r--r-- | src/backend/nodes/outfuncs.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c index f64553bbf8..2477a17cfa 100644 --- a/src/backend/nodes/outfuncs.c +++ b/src/backend/nodes/outfuncs.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.345 2008/11/15 19:43:46 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.346 2008/12/01 21:06:12 tgl Exp $ * * NOTES * Every node type that can appear in stored rules' parsetrees *must* @@ -1563,6 +1563,7 @@ _outRestrictInfo(StringInfo str, RestrictInfo *node) WRITE_BITMAPSET_FIELD(right_relids); WRITE_NODE_FIELD(orclause); /* don't write parent_ec, leads to infinite recursion in plan tree dump */ + WRITE_FLOAT_FIELD(this_selec, "%.4f"); WRITE_NODE_FIELD(mergeopfamilies); /* don't write left_ec, leads to infinite recursion in plan tree dump */ /* don't write right_ec, leads to infinite recursion in plan tree dump */ |