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Fix thinko in new match_join_clauses_to_index() logic.

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We don't need to constrain the other side of an indexable join clause to
not be below an outer join; an example here is

SELECT FROM t1 LEFT JOIN t2 ON t1.a = t2.b LEFT JOIN t3 ON t2.c = t3.d;

We can consider an inner indexscan on t3.d using c = d as indexqual, even
though t2.c is potentially nulled by a previous outer join.  The comparable
logic in orindxpath.c has always worked that way, but I was being overly
cautious here.
This commit is contained in:
Tom Lane 2012-02-28 18:10:40 -05:00
parent 973e9fb294
commit 0140a11b9b
1 changed files with 4 additions and 4 deletions
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8
src/backend/optimizer/path/indxpath.c
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@ -1702,9 +1702,9 @@ match_join_clauses_to_index(PlannerInfo *root,
* outer join rules.
*
* Instead of considering required_relids, we ignore clauses for which
* any referenced rel is in nullable_relids; that means there's an
* outer join below the clause and so it can't be checked at the
* relation scan level.
* the indexed rel is in nullable_relids; that means there's an outer
* join below the clause and so it can't be checked at the relation
* scan level.
*
* Note: unlike create_or_index_quals(), we can accept clauses that
* are marked !is_pushed_down (ie they are themselves outer-join
@ -1712,7 +1712,7 @@ match_join_clauses_to_index(PlannerInfo *root,
* could only be used in the inside of a nestloop join, which will be
* the nullable side.
*/
if (bms_overlap(rinfo->clause_relids, rinfo->nullable_relids))
if (bms_overlap(rel->relids, rinfo->nullable_relids))
continue;
/* Potentially usable, so see if it matches the index or is an OR */