From: Richard Guo Date: Tue, 9 Dec 2025 07:56:26 +0000 (+0900) Subject: Fix const-simplification for index expressions and predicate X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=c925ad30b047ec1388247539e86729d584c34b8d;p=postgresql.git Fix const-simplification for index expressions and predicate Similar to the issue with constraint and statistics expressions fixed in 317c117d6, index expressions and predicate can also suffer from incorrect reduction of NullTest clauses during const-simplification, due to unfixed varnos and the use of a NULL root. It has been reported that this issue can cause the planner to fail to pick up a partial index that it previously matched successfully. Because we need to cache the const-simplified index expressions and predicate in the relcache entry, we cannot fix the Vars before applying eval_const_expressions. To ensure proper reduction of NullTest clauses, this patch runs eval_const_expressions a second time -- after the Vars have been fixed and with a valid root. It could be argued that the additional call to eval_const_expressions might increase planning time, but I don't think that's a concern. It only runs when index expressions and predicate are present; it is relatively cheap when run on small expression trees (which is typically the case for index expressions and predicate), and it runs on expressions that have already been const-simplified once, making the second pass even cheaper. In return, in cases like the one reported, it allows the planner to match and use partial indexes, which can lead to significant execution-time improvements. Bug: #19007 Reported-by: Bryan Fox Author: Richard Guo Discussion: https://postgr.es/m/19007-4cc6e252ed8aa54a@postgresql.org --- diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c index 07f92fac239..ed0dac37f51 100644 --- a/src/backend/optimizer/util/plancat.c +++ b/src/backend/optimizer/util/plancat.c @@ -429,13 +429,32 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent, * modify the copies we obtain from the relcache to have the * correct varno for the parent relation, so that they match up * correctly against qual clauses. + * + * After fixing the varnos, we need to run the index expressions + * and predicate through const-simplification again, using a valid + * "root". This ensures that NullTest quals for Vars can be + * properly reduced. */ info->indexprs = RelationGetIndexExpressions(indexRelation); info->indpred = RelationGetIndexPredicate(indexRelation); - if (info->indexprs && varno != 1) - ChangeVarNodes((Node *) info->indexprs, 1, varno, 0); - if (info->indpred && varno != 1) - ChangeVarNodes((Node *) info->indpred, 1, varno, 0); + if (info->indexprs) + { + if (varno != 1) + ChangeVarNodes((Node *) info->indexprs, 1, varno, 0); + + info->indexprs = (List *) + eval_const_expressions(root, (Node *) info->indexprs); + } + if (info->indpred) + { + if (varno != 1) + ChangeVarNodes((Node *) info->indpred, 1, varno, 0); + + info->indpred = (List *) + eval_const_expressions(root, + (Node *) make_ands_explicit(info->indpred)); + info->indpred = make_ands_implicit((Expr *) info->indpred); + } /* Build targetlist using the completed indexprs data */ info->indextlist = build_index_tlist(root, info, relation); @@ -1047,8 +1066,13 @@ infer_arbiter_indexes(PlannerInfo *root) /* Expression attributes (if any) must match */ idxExprs = RelationGetIndexExpressions(idxRel); - if (idxExprs && varno != 1) - ChangeVarNodes((Node *) idxExprs, 1, varno, 0); + if (idxExprs) + { + if (varno != 1) + ChangeVarNodes((Node *) idxExprs, 1, varno, 0); + + idxExprs = (List *) eval_const_expressions(root, (Node *) idxExprs); + } /* * If arbiterElems are present, check them. (Note that if a @@ -1109,8 +1133,16 @@ infer_arbiter_indexes(PlannerInfo *root) continue; predExprs = RelationGetIndexPredicate(idxRel); - if (predExprs && varno != 1) - ChangeVarNodes((Node *) predExprs, 1, varno, 0); + if (predExprs) + { + if (varno != 1) + ChangeVarNodes((Node *) predExprs, 1, varno, 0); + + predExprs = (List *) + eval_const_expressions(root, + (Node *) make_ands_explicit(predExprs)); + predExprs = make_ands_implicit((Expr *) predExprs); + } /* * Partial indexes affect each form of ON CONFLICT differently: if a diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out index 0e82ca1867a..2a0a457a7d9 100644 --- a/src/test/regress/expected/join.out +++ b/src/test/regress/expected/join.out @@ -9547,7 +9547,7 @@ left join j2 on j1.id1 = j2.id1 where j1.id2 = 1; Output: j2.id1, j2.id2 (8 rows) -create unique index j1_id2_idx on j1(id2) where id2 is not null; +create unique index j1_id2_idx on j1(id2) where id2 > 0; -- ensure we don't use a partial unique index as unique proofs explain (verbose, costs off) select * from j1 diff --git a/src/test/regress/expected/predicate.out b/src/test/regress/expected/predicate.out index 66fb0854b88..94c343fe030 100644 --- a/src/test/regress/expected/predicate.out +++ b/src/test/regress/expected/predicate.out @@ -443,3 +443,44 @@ SELECT * FROM pred_tab2, pred_tab1 WHERE pred_tab1.a IS NULL OR pred_tab1.b < 2; RESET constraint_exclusion; DROP TABLE pred_tab1; DROP TABLE pred_tab2; +-- Validate that NullTest quals in index expressions and predicate are reduced correctly +CREATE TABLE pred_tab (a int, b int NOT NULL, c int NOT NULL); +INSERT INTO pred_tab SELECT i, i, i FROM generate_series(1, 1000) i; +CREATE INDEX pred_tab_exprs_idx ON pred_tab ((a < 5 AND b IS NOT NULL AND c IS NOT NULL)); +CREATE INDEX pred_tab_pred_idx ON pred_tab (a) WHERE b IS NOT NULL AND c IS NOT NULL; +ANALYZE pred_tab; +-- Ensure that index pred_tab_exprs_idx is used +EXPLAIN (COSTS OFF) +SELECT * FROM pred_tab WHERE (a < 5 AND b IS NOT NULL AND c IS NOT NULL) IS TRUE; + QUERY PLAN +------------------------------------------------- + Index Scan using pred_tab_exprs_idx on pred_tab + Index Cond: ((a < 5) = true) +(2 rows) + +SELECT * FROM pred_tab WHERE (a < 5 AND b IS NOT NULL AND c IS NOT NULL) IS TRUE; + a | b | c +---+---+--- + 1 | 1 | 1 + 2 | 2 | 2 + 3 | 3 | 3 + 4 | 4 | 4 +(4 rows) + +-- Ensure that index pred_tab_pred_idx is used +EXPLAIN (COSTS OFF) +SELECT * FROM pred_tab WHERE a < 3 AND b IS NOT NULL AND c IS NOT NULL; + QUERY PLAN +------------------------------------------------ + Index Scan using pred_tab_pred_idx on pred_tab + Index Cond: (a < 3) +(2 rows) + +SELECT * FROM pred_tab WHERE a < 3 AND b IS NOT NULL AND c IS NOT NULL; + a | b | c +---+---+--- + 1 | 1 | 1 + 2 | 2 | 2 +(2 rows) + +DROP TABLE pred_tab; diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql index c6b8b09a381..c47118e9291 100644 --- a/src/test/regress/sql/join.sql +++ b/src/test/regress/sql/join.sql @@ -3599,7 +3599,7 @@ explain (verbose, costs off) select * from j1 left join j2 on j1.id1 = j2.id1 where j1.id2 = 1; -create unique index j1_id2_idx on j1(id2) where id2 is not null; +create unique index j1_id2_idx on j1(id2) where id2 > 0; -- ensure we don't use a partial unique index as unique proofs explain (verbose, costs off) diff --git a/src/test/regress/sql/predicate.sql b/src/test/regress/sql/predicate.sql index 32302d60b6d..7d4fda1bc18 100644 --- a/src/test/regress/sql/predicate.sql +++ b/src/test/regress/sql/predicate.sql @@ -221,3 +221,22 @@ SELECT * FROM pred_tab2, pred_tab1 WHERE pred_tab1.a IS NULL OR pred_tab1.b < 2; RESET constraint_exclusion; DROP TABLE pred_tab1; DROP TABLE pred_tab2; + +-- Validate that NullTest quals in index expressions and predicate are reduced correctly +CREATE TABLE pred_tab (a int, b int NOT NULL, c int NOT NULL); +INSERT INTO pred_tab SELECT i, i, i FROM generate_series(1, 1000) i; +CREATE INDEX pred_tab_exprs_idx ON pred_tab ((a < 5 AND b IS NOT NULL AND c IS NOT NULL)); +CREATE INDEX pred_tab_pred_idx ON pred_tab (a) WHERE b IS NOT NULL AND c IS NOT NULL; +ANALYZE pred_tab; + +-- Ensure that index pred_tab_exprs_idx is used +EXPLAIN (COSTS OFF) +SELECT * FROM pred_tab WHERE (a < 5 AND b IS NOT NULL AND c IS NOT NULL) IS TRUE; +SELECT * FROM pred_tab WHERE (a < 5 AND b IS NOT NULL AND c IS NOT NULL) IS TRUE; + +-- Ensure that index pred_tab_pred_idx is used +EXPLAIN (COSTS OFF) +SELECT * FROM pred_tab WHERE a < 3 AND b IS NOT NULL AND c IS NOT NULL; +SELECT * FROM pred_tab WHERE a < 3 AND b IS NOT NULL AND c IS NOT NULL; + +DROP TABLE pred_tab;