postgres.git / summary / log / commit / refs
commit e3bd026fbb91c64e99c2a66eceb2dba3cc3ec6f0
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon Oct 05 17:15:40 2020 +0000
First released in: 14.0, 9.5.24, 9.6.20, 10.15, 11.10, 12.5, 13.1
Fix two latent(?) bugs in equivclass.c.
get_eclass_for_sort_expr() computes expr_relids and nullable_relids
early on, even though they won't be needed unless we make a new
EquivalenceClass, which we often don't. Aside from the probably-minor
inefficiency, there's a memory management problem: these bitmapsets will
be built in the caller's context, leading to dangling pointers if that
is shorter-lived than root->planner_cxt. This would be a live bug if
get_eclass_for_sort_expr() could be called with create_it = true during
GEQO join planning. So far as I can find, the core code never does
that, but it's hard to be sure that no extensions do, especially since
the comments make it clear that that's supposed to be a supported case.
Fix by not computing these values until we've switched into planner_cxt
to build the new EquivalenceClass.
generate_join_implied_equalities() uses inner_rel->relids to look up
relevant eclasses, but it ought to be using nominal_inner_relids.
This is presently harmless because a child RelOptInfo will always have
exactly the same eclass_indexes as its topmost parent; but that might
not be true forever, and anyway it makes the code confusing.
The first of these is old (introduced by me in f3b3b8d5b), so back-patch
to all supported branches. The second only dates to v13, but we might
as well back-patch it to keep the code looking similar across branches.
Discussion: https://postgr.es/m/1508010.1601832581@sss.pgh.pa.us
src/backend/optimizer/path/equivclass.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c
index 9408feacb8e..2e23ab673fa 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -565,12 +565,6 @@ get_eclass_for_sort_expr(PlannerInfo *root,
*/
expr = canonicalize_ec_expression(expr, opcintype, collation);
- /*
- * Get the precise set of nullable relids appearing in the expression.
- */
- expr_relids = pull_varnos((Node *) expr);
- nullable_relids = bms_intersect(nullable_relids, expr_relids);
-
/*
* Scan through the existing EquivalenceClasses for a match
*/
@@ -645,6 +639,12 @@ get_eclass_for_sort_expr(PlannerInfo *root,
if (newec->ec_has_volatile && sortref == 0) /* should not happen */
elog(ERROR, "volatile EquivalenceClass has no sortref");
+ /*
+ * Get the precise set of nullable relids appearing in the expression.
+ */
+ expr_relids = pull_varnos((Node *) expr);
+ nullable_relids = bms_intersect(nullable_relids, expr_relids);
+
newem = add_eq_member(newec, copyObject(expr), expr_relids,
nullable_relids, false, opcintype);
[parent: d40a00003621]