diff options
Diffstat (limited to 'src/backend/optimizer/plan/initsplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/initsplan.c | 28 |
1 files changed, 13 insertions, 15 deletions
diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c index 40a867c2607..2f4e8181eb5 100644 --- a/src/backend/optimizer/plan/initsplan.c +++ b/src/backend/optimizer/plan/initsplan.c @@ -1129,17 +1129,6 @@ make_outerjoininfo(PlannerInfo *root, right_rels); /* - * If we have a degenerate join clause that doesn't mention any RHS rels, - * force the min RHS to be the syntactic RHS; otherwise we can end up - * making serious errors, like putting the LHS on the wrong side of an - * outer join. It seems to be safe to not do this when we have a - * contribution from inner_join_rels, though; that's enough to pin the SJ - * to occur at a reasonable place in the tree. - */ - if (bms_is_empty(min_righthand)) - min_righthand = bms_copy(right_rels); - - /* * Now check previous outer joins for ordering restrictions. */ foreach(l, root->join_info_list) @@ -1181,9 +1170,15 @@ make_outerjoininfo(PlannerInfo *root, * For a lower OJ in our RHS, if our join condition does not use the * lower join's RHS and the lower OJ's join condition is strict, we * can interchange the ordering of the two OJs; otherwise we must add - * the lower OJ's full syntactic relset to min_righthand. Also, we - * must preserve ordering anyway if either the current join or the - * lower OJ is either a semijoin or an antijoin. + * the lower OJ's full syntactic relset to min_righthand. + * + * Also, if our join condition does not use the lower join's LHS + * either, force the ordering to be preserved. Otherwise we can end + * up with SpecialJoinInfos with identical min_righthands, which can + * confuse join_is_legal (see discussion in backend/optimizer/README). + * + * Also, we must preserve ordering anyway if either the current join + * or the lower OJ is either a semijoin or an antijoin. * * Here, we have to consider that "our join condition" includes any * clauses that syntactically appeared above the lower OJ and below @@ -1199,6 +1194,7 @@ make_outerjoininfo(PlannerInfo *root, if (bms_overlap(right_rels, otherinfo->syn_righthand)) { if (bms_overlap(clause_relids, otherinfo->syn_righthand) || + !bms_overlap(clause_relids, otherinfo->min_lefthand) || jointype == JOIN_SEMI || jointype == JOIN_ANTI || otherinfo->jointype == JOIN_SEMI || @@ -1238,10 +1234,12 @@ make_outerjoininfo(PlannerInfo *root, * If we found nothing to put in min_lefthand, punt and make it the full * LHS, to avoid having an empty min_lefthand which will confuse later * processing. (We don't try to be smart about such cases, just correct.) - * We already forced min_righthand nonempty, so nothing to do for that. + * Likewise for min_righthand. */ if (bms_is_empty(min_lefthand)) min_lefthand = bms_copy(left_rels); + if (bms_is_empty(min_righthand)) + min_righthand = bms_copy(right_rels); /* Now they'd better be nonempty */ Assert(!bms_is_empty(min_lefthand)); |