From 173a6760278f4c25aaa41c3ed70bae6fecb732aa Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 8 Dec 2008 00:16:09 +0000 Subject: [PATCH] Don't try to optimize EXISTS subqueries with empty FROM-lists: we need to form a join and that case doesn't have anything to join to. (We could probably make it work if we didn't pull up the subquery, but it seems to me that the case isn't worth extra code.) Per report from Greg Stark. --- src/backend/optimizer/plan/subselect.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c index b80427f041..c999fb6419 100644 --- a/src/backend/optimizer/plan/subselect.c +++ b/src/backend/optimizer/plan/subselect.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.142 2008/10/21 20:42:53 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.143 2008/12/08 00:16:09 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1097,6 +1097,12 @@ convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink, if (!simplify_EXISTS_query(subselect)) return false; + /* + * The subquery must have a nonempty jointree, else we won't have a join. + */ + if (subselect->jointree->fromlist == NIL) + return false; + /* * Separate out the WHERE clause. (We could theoretically also remove * top-level plain JOIN/ON clauses, but it's probably not worth the @@ -1180,6 +1186,7 @@ convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink, /* Identify all the rels syntactically within the subselect */ subselect_varnos = get_relids_in_jointree((Node *) subselect->jointree, true); + Assert(!bms_is_empty(subselect_varnos)); Assert(bms_is_subset(right_varnos, subselect_varnos)); /* Now we can attach the modified subquery rtable to the parent */