diff options
Diffstat (limited to 'src/backend/optimizer/plan/analyzejoins.c')
| -rw-r--r-- | src/backend/optimizer/plan/analyzejoins.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c index 6b58567f511..be19167e4a2 100644 --- a/src/backend/optimizer/plan/analyzejoins.c +++ b/src/backend/optimizer/plan/analyzejoins.c @@ -403,7 +403,12 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel, /* * Likewise remove references from PlaceHolderVar data structures, - * removing any no-longer-needed placeholders entirely. + * removing any no-longer-needed placeholders entirely. We remove PHV + * only for left-join removal. With self-join elimination, PHVs already + * get moved to the remaining relation, where they might still be needed. + * It might also happen that we skip the removal of some PHVs that could + * be removed. However, the overhead of extra PHVs is small compared to + * the complexity of analysis needed to remove them. * * Removal is a bit trickier than it might seem: we can remove PHVs that * are used at the target rel and/or in the join qual, but not those that @@ -420,10 +425,16 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel, PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l); Assert(sjinfo == NULL || !bms_is_member(relid, phinfo->ph_lateral)); - if (bms_is_subset(phinfo->ph_needed, joinrelids) && + if (sjinfo != NULL && + bms_is_subset(phinfo->ph_needed, joinrelids) && bms_is_member(relid, phinfo->ph_eval_at) && - (sjinfo == NULL || !bms_is_member(sjinfo->ojrelid, phinfo->ph_eval_at))) + !bms_is_member(sjinfo->ojrelid, phinfo->ph_eval_at)) { + /* + * This code shouldn't be executed if one relation is substituted + * with another: in this case, the placeholder may be employed in + * a filter inside the scan node the SJE removes. + */ root->placeholder_list = foreach_delete_current(root->placeholder_list, l); root->placeholder_array[phinfo->phid] = NULL; |