diff options
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 27 |
1 files changed, 17 insertions, 10 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 350fde29c21..49e8a1222aa 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 1.101 2009/07/19 20:32:48 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.102 2009/07/23 17:42:06 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -400,6 +400,22 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, continue; /* + * If it's a semijoin and we already joined the RHS to any other + * rels within either input, then we must have unique-ified the RHS + * at that point (see below). Therefore the semijoin is no longer + * relevant in this join path. + */ + if (sjinfo->jointype == JOIN_SEMI) + { + if (bms_is_subset(sjinfo->syn_righthand, rel1->relids) && + !bms_equal(sjinfo->syn_righthand, rel1->relids)) + continue; + if (bms_is_subset(sjinfo->syn_righthand, rel2->relids) && + !bms_equal(sjinfo->syn_righthand, rel2->relids)) + continue; + } + + /* * If one input contains min_lefthand and the other contains * min_righthand, then we can perform the SJ at this join. * @@ -491,9 +507,6 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, * We assume that make_outerjoininfo() set things up correctly * so that we'll only match to some SJ if the join is valid. * Set flag here to check at bottom of loop. - * - * For a semijoin, assume it's okay if either side fully contains - * the RHS (per the unique-ification case above). *---------- */ if (sjinfo->jointype != JOIN_SEMI && @@ -503,12 +516,6 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, /* seems OK */ Assert(!bms_overlap(joinrelids, sjinfo->min_lefthand)); } - else if (sjinfo->jointype == JOIN_SEMI && - (bms_is_subset(sjinfo->syn_righthand, rel1->relids) || - bms_is_subset(sjinfo->syn_righthand, rel2->relids))) - { - /* seems OK */ - } else is_valid_inner = false; } |