diff options
Diffstat (limited to 'src/backend/optimizer/util/joininfo.c')
| -rw-r--r-- | src/backend/optimizer/util/joininfo.c | 39 |
1 files changed, 37 insertions, 2 deletions
diff --git a/src/backend/optimizer/util/joininfo.c b/src/backend/optimizer/util/joininfo.c index 9aab37753de..bd54a1384b4 100644 --- a/src/backend/optimizer/util/joininfo.c +++ b/src/backend/optimizer/util/joininfo.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/util/joininfo.c,v 1.44 2006/03/05 15:58:31 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/util/joininfo.c,v 1.45 2006/12/12 21:31:02 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -24,7 +24,8 @@ * the two given relations. */ bool -have_relevant_joinclause(RelOptInfo *rel1, RelOptInfo *rel2) +have_relevant_joinclause(PlannerInfo *root, + RelOptInfo *rel1, RelOptInfo *rel2) { bool result = false; Relids join_relids; @@ -53,6 +54,40 @@ have_relevant_joinclause(RelOptInfo *rel1, RelOptInfo *rel2) } } + /* + * It's possible that the rels correspond to the left and right sides + * of a degenerate outer join, that is, one with no joinclause mentioning + * the non-nullable side. The above scan will then have failed to locate + * any joinclause indicating we should join, but nonetheless we must + * allow the join to occur. + * + * Note: we need no comparable check for IN-joins because we can handle + * sequential buildup of an IN-join to multiple outer-side rels; therefore + * the "last ditch" case in make_rels_by_joins() always succeeds. We + * could dispense with this hack if we were willing to try bushy plans + * in the "last ditch" case, but that seems too expensive. + */ + if (!result) + { + foreach(l, root->oj_info_list) + { + OuterJoinInfo *ojinfo = (OuterJoinInfo *) lfirst(l); + + /* ignore full joins --- other mechanisms handle them */ + if (ojinfo->is_full_join) + continue; + + if ((bms_is_subset(ojinfo->min_lefthand, rel1->relids) && + bms_is_subset(ojinfo->min_righthand, rel2->relids)) || + (bms_is_subset(ojinfo->min_lefthand, rel2->relids) && + bms_is_subset(ojinfo->min_righthand, rel1->relids))) + { + result = true; + break; + } + } + } + bms_free(join_relids); return result; |