From b8bfc22f919f03d63c809cb15c22f9c78e2b9d75 Mon Sep 17 00:00:00 2001 From: Ilia Evdokimov Date: Mon, 17 Aug 2026 14:10:45 +0300 Subject: [PATCH v1] Use extended statistics for join clauses during parameterized costing Dependency-based extended statistics were only considered when every clause in a clause list referenced a single relation. When costing a parameterized inner path of a nested loop join, one side of an equality clause is a Var belonging to the outer relation, so the whole clause list was rejected by dependency_is_compatible_clause() and the planner fell back to the default per-column independence assumption - even though the parameterized relation's own extended statistics could produce a much better estimate. Teach dependency_is_compatible_clause() to also accept clauses of the form "relid.a = otherrel.b": the other relation's Var is treated like a pseudoconstant for compatibility-checking purposes, since its value is fixed for the duration of one parameterized probe and the degree-based estimate does not depend on it. The degree lookup and combination logic itself is unchanged. --- src/backend/optimizer/path/clausesel.c | 10 ++++++++ src/backend/statistics/dependencies.c | 35 +++++++++++++++++++++++--- 2 files changed, 42 insertions(+), 3 deletions(-) diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c index 25c4d177ad9..57a370d5b14 100644 --- a/src/backend/optimizer/path/clausesel.c +++ b/src/backend/optimizer/path/clausesel.c @@ -155,6 +155,16 @@ clauselist_selectivity_ext(PlannerInfo *root, &estimatedclauses, false); } + if (use_extended_stats && rel == NULL && varRelid != 0) + { + RelOptInfo *paramrel = find_base_rel(root, varRelid); + + if (paramrel->rtekind == RTE_RELATION && paramrel->statlist != NIL) + s1 *= dependencies_clauselist_selectivity(root, clauses, varRelid, + jointype, sjinfo, paramrel, + &estimatedclauses); + } + /* * Apply normal selectivity estimates for remaining clauses. We'll be * careful to skip any clauses which were already estimated above. diff --git a/src/backend/statistics/dependencies.c b/src/backend/statistics/dependencies.c index 81bcf76cc1c..211100b1547 100644 --- a/src/backend/statistics/dependencies.c +++ b/src/backend/statistics/dependencies.c @@ -734,8 +734,14 @@ dependency_is_compatible_clause(Node *clause, Index relid, AttrNumber *attnum) if (rinfo->pseudoconstant) return false; - /* Clauses referencing multiple, or no, varnos are incompatible */ - if (bms_membership(rinfo->clause_relids) != BMS_SINGLETON) + /* + * Clauses referencing more than two, or no, varnos are incompatible. + * A second varno is allowed because we also accept "relid's Var = + * other relation's Var" below, e.g. a parameterized index qual like + * "t1.a = t2.b" while costing an index scan on t1. + */ + if (bms_num_members(rinfo->clause_relids) > 2 || + bms_num_members(rinfo->clause_relids) == 0) return false; clause = (Node *) rinfo->clause; @@ -756,7 +762,30 @@ dependency_is_compatible_clause(Node *clause, Index relid, AttrNumber *attnum) else if (is_pseudo_constant_clause(linitial(expr->args))) clause_expr = lsecond(expr->args); else - return false; + { + /* + * Neither argument is a pseudoconstant, but this can still be a + * usable equality clause when costing a parameterized path: one + * argument is a Var of "relid" and the other is a Var of some + * other single relation, which is fixed for the duration of one + * parameterized scan and can be treated like a constant. + */ + Bitmapset *largrelids = pull_varnos(NULL, linitial(expr->args)); + Bitmapset *rargrelids = pull_varnos(NULL, lsecond(expr->args)); + + if (bms_membership(largrelids) == BMS_SINGLETON && + bms_singleton_member(largrelids) == relid && + bms_membership(rargrelids) == BMS_SINGLETON && + bms_singleton_member(rargrelids) != relid) + clause_expr = linitial(expr->args); + else if (bms_membership(rargrelids) == BMS_SINGLETON && + bms_singleton_member(rargrelids) == relid && + bms_membership(largrelids) == BMS_SINGLETON && + bms_singleton_member(largrelids) != relid) + clause_expr = lsecond(expr->args); + else + return false; + } /* * If it's not an "=" operator, just ignore the clause, as it's not -- 2.34.1