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Tighten up join ordering rules to account for recent more-careful analysis

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of the associativity of antijoins.  Also improve optimizer/README discussion
of outer join ordering rules.
This commit is contained in:
Tom Lane
2009-02-27 22:41:38 +00:00
parent 5c4ca3b632
commit 75c85bd199
3 changed files with 38 additions and 19 deletions
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27
src/backend/optimizer/plan/initsplan.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.148 2009/02/25 03:30:37 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.149 2009/02/27 22:41:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -628,26 +628,32 @@ make_outerjoininfo(PlannerInfo *root,
* min_lefthand. (We must use its full syntactic relset, not just its
* min_lefthand + min_righthand. This is because there might be other
* OJs below this one that this one can commute with, but we cannot
* commute with them if we don't with this one.)
* commute with them if we don't with this one.) Also, if the
* current join is an antijoin, we must preserve ordering regardless
* of strictness.
*
* Note: I believe we have to insist on being strict for at least one
* rel in the lower OJ's min_righthand, not its whole syn_righthand.
*/
if (bms_overlap(left_rels, otherinfo->syn_righthand) &&
bms_overlap(clause_relids, otherinfo->syn_righthand) &&
!bms_overlap(strict_relids, otherinfo->min_righthand))
if (bms_overlap(left_rels, otherinfo->syn_righthand))
{
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_lefthand);
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_righthand);
if (bms_overlap(clause_relids, otherinfo->syn_righthand) &&
(jointype == JOIN_ANTI ||
!bms_overlap(strict_relids, otherinfo->min_righthand)))
{
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_lefthand);
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_righthand);
}
}
/*
* For a lower OJ in our RHS, if our join condition does not use the
* lower join's RHS and the lower OJ's join condition is strict, we
* can interchange the ordering of the two OJs; otherwise we must add
* lower OJ's full syntactic relset to min_righthand.
* lower OJ's full syntactic relset to min_righthand. Here, we must
* preserve ordering anyway if the lower OJ is an antijoin.
*
* Here, we have to consider that "our join condition" includes any
* clauses that syntactically appeared above the lower OJ and below
@@ -663,6 +669,7 @@ make_outerjoininfo(PlannerInfo *root,
if (bms_overlap(right_rels, otherinfo->syn_righthand))
{
if (bms_overlap(clause_relids, otherinfo->syn_righthand) ||
otherinfo->jointype == JOIN_ANTI ||
!otherinfo->lhs_strict || otherinfo->delay_upper_joins)
{
min_righthand = bms_add_members(min_righthand,