diff options
Diffstat (limited to 'src/backend/optimizer/path/joinrels.c')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index b2cc9f07f56..9f0212fad23 100644 --- a/src/backend/optimizer/path/joinrels.c +++ b/src/backend/optimizer/path/joinrels.c @@ -334,6 +334,7 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, bool must_be_leftjoin; bool lateral_fwd; bool lateral_rev; + Relids join_lateral_rels; ListCell *l; /* @@ -569,6 +570,35 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, } } + /* + * LATERAL references could also cause problems later on if we accept this + * join: if the join's minimum parameterization includes any rels that + * would have to be on the inside of an outer join with this join rel, + * then it's never going to be possible to build the complete query using + * this join. We should reject this join not only because it'll save + * work, but because if we don't, the clauseless-join heuristics might + * think that legality of this join means that some other join rel need + * not be formed, and that could lead to failure to find any plan at all. + * It seems best not to merge this check into the main loop above, because + * it is concerned with SJs that are not otherwise relevant to this join. + */ + join_lateral_rels = min_join_parameterization(root, joinrelids); + if (join_lateral_rels) + { + foreach(l, root->join_info_list) + { + SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l); + + if (bms_overlap(sjinfo->min_righthand, join_lateral_rels) && + bms_overlap(sjinfo->min_lefthand, joinrelids)) + return false; /* will not be able to join to min_righthand */ + if (sjinfo->jointype == JOIN_FULL && + bms_overlap(sjinfo->min_lefthand, join_lateral_rels) && + bms_overlap(sjinfo->min_righthand, joinrelids)) + return false; /* will not be able to join to min_lefthand */ + } + } + /* Otherwise, it's a valid join */ *sjinfo_p = match_sjinfo; *reversed_p = reversed; |