diff options
Diffstat (limited to 'src/backend')
| -rw-r--r-- | src/backend/optimizer/path/equivclass.c | 28 |
1 files changed, 20 insertions, 8 deletions
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c index f962ff82ad2..e65b967b1f0 100644 --- a/src/backend/optimizer/path/equivclass.c +++ b/src/backend/optimizer/path/equivclass.c @@ -1382,7 +1382,9 @@ generate_base_implied_equalities_broken(PlannerInfo *root, * whenever we select a particular pair of EquivalenceMembers to join, * we check to see if the pair matches any original clause (in ec_sources) * or previously-built clause (in ec_derives). This saves memory and allows - * re-use of information cached in RestrictInfos. + * re-use of information cached in RestrictInfos. We also avoid generating + * commutative duplicates, i.e. if the algorithm selects "a.x = b.y" but + * we already have "b.y = a.x", we return the existing clause. * * join_relids should always equal bms_union(outer_relids, inner_rel->relids). * We could simplify this function's API by computing it internally, but in @@ -1790,7 +1792,8 @@ select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype) /* * create_join_clause * Find or make a RestrictInfo comparing the two given EC members - * with the given operator. + * with the given operator (or, possibly, its commutator, because + * the ordering of the operands in the result is not guaranteed). * * parent_ec is either equal to ec (if the clause is a potentially-redundant * join clause) or NULL (if not). We have to treat this as part of the @@ -1811,16 +1814,22 @@ create_join_clause(PlannerInfo *root, /* * Search to see if we already built a RestrictInfo for this pair of * EquivalenceMembers. We can use either original source clauses or - * previously-derived clauses. The check on opno is probably redundant, - * but be safe ... + * previously-derived clauses, and a commutator clause is acceptable. + * + * We used to verify that opno matches, but that seems redundant: even if + * it's not identical, it'd better have the same effects, or the operator + * families we're using are broken. */ foreach(lc, ec->ec_sources) { rinfo = (RestrictInfo *) lfirst(lc); if (rinfo->left_em == leftem && rinfo->right_em == rightem && - rinfo->parent_ec == parent_ec && - opno == ((OpExpr *) rinfo->clause)->opno) + rinfo->parent_ec == parent_ec) + return rinfo; + if (rinfo->left_em == rightem && + rinfo->right_em == leftem && + rinfo->parent_ec == parent_ec) return rinfo; } @@ -1829,8 +1838,11 @@ create_join_clause(PlannerInfo *root, rinfo = (RestrictInfo *) lfirst(lc); if (rinfo->left_em == leftem && rinfo->right_em == rightem && - rinfo->parent_ec == parent_ec && - opno == ((OpExpr *) rinfo->clause)->opno) + rinfo->parent_ec == parent_ec) + return rinfo; + if (rinfo->left_em == rightem && + rinfo->right_em == leftem && + rinfo->parent_ec == parent_ec) return rinfo; } |