diff options
Diffstat (limited to 'src/backend/optimizer/path/joinrels.c')
| -rw-r--r-- | src/backend/optimizer/path/joinrels.c | 60 |
1 files changed, 0 insertions, 60 deletions
diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c index 60d65762b5d..aad41b94009 100644 --- a/src/backend/optimizer/path/joinrels.c +++ b/src/backend/optimizer/path/joinrels.c @@ -565,9 +565,6 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, * Also, if the lateral reference is only indirect, we should reject * the join; whatever rel(s) the reference chain goes through must be * joined to first. - * - * Another case that might keep us from building a valid plan is the - * implementation restriction described by have_dangerous_phv(). */ lateral_fwd = bms_overlap(rel1->relids, rel2->lateral_relids); lateral_rev = bms_overlap(rel2->relids, rel1->lateral_relids); @@ -584,9 +581,6 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, /* check there is a direct reference from rel2 to rel1 */ if (!bms_overlap(rel1->relids, rel2->direct_lateral_relids)) return false; /* only indirect refs, so reject */ - /* check we won't have a dangerous PHV */ - if (have_dangerous_phv(root, rel1->relids, rel2->lateral_relids)) - return false; /* might be unable to handle required PHV */ } else if (lateral_rev) { @@ -599,9 +593,6 @@ join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, /* check there is a direct reference from rel1 to rel2 */ if (!bms_overlap(rel2->relids, rel1->direct_lateral_relids)) return false; /* only indirect refs, so reject */ - /* check we won't have a dangerous PHV */ - if (have_dangerous_phv(root, rel2->relids, rel1->lateral_relids)) - return false; /* might be unable to handle required PHV */ } /* @@ -1279,57 +1270,6 @@ has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel) /* - * There's a pitfall for creating parameterized nestloops: suppose the inner - * rel (call it A) has a parameter that is a PlaceHolderVar, and that PHV's - * minimum eval_at set includes the outer rel (B) and some third rel (C). - * We might think we could create a B/A nestloop join that's parameterized by - * C. But we would end up with a plan in which the PHV's expression has to be - * evaluated as a nestloop parameter at the B/A join; and the executor is only - * set up to handle simple Vars as NestLoopParams. Rather than add complexity - * and overhead to the executor for such corner cases, it seems better to - * forbid the join. (Note that we can still make use of A's parameterized - * path with pre-joined B+C as the outer rel. have_join_order_restriction() - * ensures that we will consider making such a join even if there are not - * other reasons to do so.) - * - * So we check whether any PHVs used in the query could pose such a hazard. - * We don't have any simple way of checking whether a risky PHV would actually - * be used in the inner plan, and the case is so unusual that it doesn't seem - * worth working very hard on it. - * - * This needs to be checked in two places. If the inner rel's minimum - * parameterization would trigger the restriction, then join_is_legal() should - * reject the join altogether, because there will be no workable paths for it. - * But joinpath.c has to check again for every proposed nestloop path, because - * the inner path might have more than the minimum parameterization, causing - * some PHV to be dangerous for it that otherwise wouldn't be. - */ -bool -have_dangerous_phv(PlannerInfo *root, - Relids outer_relids, Relids inner_params) -{ - ListCell *lc; - - foreach(lc, root->placeholder_list) - { - PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc); - - if (!bms_is_subset(phinfo->ph_eval_at, inner_params)) - continue; /* ignore, could not be a nestloop param */ - if (!bms_overlap(phinfo->ph_eval_at, outer_relids)) - continue; /* ignore, not relevant to this join */ - if (bms_is_subset(phinfo->ph_eval_at, outer_relids)) - continue; /* safe, it can be eval'd within outerrel */ - /* Otherwise, it's potentially unsafe, so reject the join */ - return true; - } - - /* OK to perform the join */ - return false; -} - - -/* * is_dummy_rel --- has relation been proven empty? */ bool |