diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 5f49ee7e290..5f2123defc5 100644 --- a/src/backend/optimizer/path/joinrels.c +++ b/src/backend/optimizer/path/joinrels.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.95 2008/11/22 22:47:06 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.96 2008/11/28 19:29:07 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -420,11 +420,13 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, reversed = true; } else if (sjinfo->jointype == JOIN_SEMI && - bms_equal(sjinfo->syn_righthand, rel2->relids)) + bms_equal(sjinfo->syn_righthand, rel2->relids) && + create_unique_path(root, rel2, rel2->cheapest_total_path, + sjinfo) != NULL) { /* * For a semijoin, we can join the RHS to anything else by - * unique-ifying the RHS. + * unique-ifying the RHS (if the RHS can be unique-ified). */ if (match_sjinfo) return false; /* invalid join path */ @@ -432,7 +434,9 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, reversed = false; } else if (sjinfo->jointype == JOIN_SEMI && - bms_equal(sjinfo->syn_righthand, rel1->relids)) + bms_equal(sjinfo->syn_righthand, rel1->relids) && + create_unique_path(root, rel1, rel1->cheapest_total_path, + sjinfo) != NULL) { /* Reversed semijoin case */ if (match_sjinfo) @@ -664,7 +668,10 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2) /* * If we know how to unique-ify the RHS and one input rel is * exactly the RHS (not a superset) we can consider unique-ifying - * it and then doing a regular join. + * it and then doing a regular join. (The create_unique_path + * check here is probably redundant with what join_is_legal did, + * but if so the check is cheap because it's cached. So test + * anyway to be sure.) */ if (bms_equal(sjinfo->syn_righthand, rel2->relids) && create_unique_path(root, rel2, rel2->cheapest_total_path, |