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Fix EquivalenceClass processing for nested append relations.

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The original coding of EquivalenceClasses didn't foresee that appendrel
child relations might themselves be appendrels; but this is possible for
example when a UNION ALL subquery scans a table with inheritance children.
The oversight led to failure to optimize ordering-related issues very well
for the grandchild tables.  After some false starts involving explicitly
flattening the appendrel representation, we found that this could be fixed
easily by removing a few implicit assumptions about appendrel parent rels
not being children themselves.

Kyotaro Horiguchi and Tom Lane, reviewed by Noah Misch
This commit is contained in:
Tom Lane
2014-03-28 11:50:01 -04:00
parent b777be0d48
commit a87c729153
5 changed files with 101 additions and 9 deletions
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12
src/backend/optimizer/path/equivclass.c
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@@ -1937,16 +1937,20 @@ add_child_rel_equivalences(PlannerInfo *root,
if (cur_ec->ec_has_volatile)
continue;
/* No point in searching if parent rel not mentioned in eclass */
if (!bms_is_subset(parent_rel->relids, cur_ec->ec_relids))
/*
* No point in searching if parent rel not mentioned in eclass; but
* we can't tell that for sure if parent rel is itself a child.
*/
if (parent_rel->reloptkind == RELOPT_BASEREL &&
!bms_is_subset(parent_rel->relids, cur_ec->ec_relids))
continue;
foreach(lc2, cur_ec->ec_members)
{
EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
if (cur_em->em_is_const || cur_em->em_is_child)
continue; /* ignore consts and children here */
if (cur_em->em_is_const)
continue; /* ignore consts here */
/* Does it reference parent_rel? */
if (bms_overlap(cur_em->em_relids, parent_rel->relids))