From 9d36b883bfaaeee04f09101c5e7cde96906a256e Mon Sep 17 00:00:00 2001 From: David Rowley Date: Wed, 1 May 2024 16:35:05 +1200 Subject: [PATCH] Disable run condition optimization for some WindowFuncs 94985c210 added code to detect when WindowFuncs were monotonic and allowed additional quals to be "pushed down" into the subquery to be used as WindowClause runConditions in order to short-circuit execution in nodeWindowAgg.c. The Node representation of runConditions wasn't well selected and because we do qual pushdown before planning the subquery, the planning of the subquery could perform subquery pull-up of nested subqueries. For WindowFuncs with args, the arguments could be changed after pushing the qual down to the subquery. This was made more difficult by the fact that the code duplicated the WindowFunc inside an OpExpr to include in the WindowClauses runCondition field. This could result in duplication of subqueries and a pull-up of such a subquery could result in another initplan parameter being issued for the 2nd version of the subplan. This could result in errors such as: ERROR: WindowFunc not found in subplan target lists Here in the backbranches, we don't have the flexibility to improve the Node representation to resolve this, so instead we just disable the runCondition optimization for ntile() unless the argument is a Const, (v16 only) and likewise for count(expr) (both v15 and v16). count(*) is unaffected. All other window functions which support this optimization all take zero arguments and therefore are unaffected. Bug: #18170 Reported-by: Zuming Jiang Discussion: https://postgr.es/m/18170-f1d17bf9a0d58b24@postgresql.org Backpatch-through 15 (master will be fixed independently) --- src/backend/utils/adt/int8.c | 15 +++++ src/backend/utils/adt/windowfuncs.c | 29 +++++++-- src/test/regress/expected/window.out | 94 +++++++++++++++------------- src/test/regress/sql/window.sql | 43 ++++++++----- 4 files changed, 116 insertions(+), 65 deletions(-) diff --git a/src/backend/utils/adt/int8.c b/src/backend/utils/adt/int8.c index 123b4eb6bf..41fbeec8fd 100644 --- a/src/backend/utils/adt/int8.c +++ b/src/backend/utils/adt/int8.c @@ -833,6 +833,21 @@ int8inc_support(PG_FUNCTION_ARGS) SupportRequestWFuncMonotonic *req = (SupportRequestWFuncMonotonic *) rawreq; MonotonicFunction monotonic = MONOTONICFUNC_NONE; int frameOptions = req->window_clause->frameOptions; + WindowFunc *wfunc = req->window_func; + + if (list_length(wfunc->args) == 1) + { + Node *expr = eval_const_expressions(NULL, linitial(wfunc->args)); + + /* + * Due to the Node representation of WindowClause runConditions in + * version prior to v17, we need to insist that the count arg is + * Const to allow safe application of the runCondition + * optimization. + */ + if (!IsA(expr, Const)) + PG_RETURN_POINTER(NULL); + } /* No ORDER BY clause then all rows are peers */ if (req->window_clause->orderClause == NIL) diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c index b87a624fb2..0c7cc55845 100644 --- a/src/backend/utils/adt/windowfuncs.c +++ b/src/backend/utils/adt/windowfuncs.c @@ -14,6 +14,7 @@ #include "postgres.h" #include "nodes/supportnodes.h" +#include "optimizer/optimizer.h" #include "utils/builtins.h" #include "windowapi.h" @@ -486,13 +487,29 @@ window_ntile_support(PG_FUNCTION_ARGS) if (IsA(rawreq, SupportRequestWFuncMonotonic)) { SupportRequestWFuncMonotonic *req = (SupportRequestWFuncMonotonic *) rawreq; + WindowFunc *wfunc = req->window_func; - /* - * ntile() is monotonically increasing as the number of buckets cannot - * change after the first call - */ - req->monotonic = MONOTONICFUNC_INCREASING; - PG_RETURN_POINTER(req); + if (list_length(wfunc->args) == 1) + { + Node *expr = eval_const_expressions(NULL, linitial(wfunc->args)); + + /* + * Due to the Node representation of WindowClause runConditions in + * version prior to v17, we need to insist that ntile arg is Const + * to allow safe application of the runCondition optimization. + */ + if (IsA(expr, Const)) + { + /* + * ntile() is monotonically increasing as the number of + * buckets cannot change after the first call + */ + req->monotonic = MONOTONICFUNC_INCREASING; + PG_RETURN_POINTER(req); + } + } + + PG_RETURN_POINTER(NULL); } if (IsA(rawreq, SupportRequestOptimizeWindowClause)) diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out index 8612788702..1a9cc66a6b 100644 --- a/src/test/regress/expected/window.out +++ b/src/test/regress/expected/window.out @@ -3577,13 +3577,13 @@ EXPLAIN (COSTS OFF) SELECT * FROM (SELECT empno, salary, - count(empno) OVER (ORDER BY salary DESC) c + count(1) OVER (ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; - QUERY PLAN ---------------------------------------------------------- + QUERY PLAN +------------------------------------------- WindowAgg - Run Condition: (count(empsalary.empno) OVER (?) <= 3) + Run Condition: (count(1) OVER (?) <= 3) -> Sort Sort Key: empsalary.salary DESC -> Seq Scan on empsalary @@ -3592,7 +3592,7 @@ WHERE c <= 3; SELECT * FROM (SELECT empno, salary, - count(empno) OVER (ORDER BY salary DESC) c + count(1) OVER (ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; empno | salary | c @@ -3704,19 +3704,19 @@ WHERE rn < 3; -> Seq Scan on empsalary (6 rows) --- likewise with count(empno) instead of row_number() +-- likewise with count(1) instead of row_number() EXPLAIN (COSTS OFF) SELECT * FROM (SELECT empno, depname, salary, - count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c + count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; QUERY PLAN ------------------------------------------------------------ WindowAgg - Run Condition: (count(empsalary.empno) OVER (?) <= 3) + Run Condition: (count(1) OVER (?) <= 3) -> Sort Sort Key: empsalary.depname, empsalary.salary DESC -> Seq Scan on empsalary @@ -3727,7 +3727,7 @@ SELECT * FROM (SELECT empno, depname, salary, - count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c + count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; empno | depname | salary | c @@ -3749,13 +3749,13 @@ SELECT * FROM (SELECT empno, depname, salary, - count(empno) OVER () c + count(1) OVER () c FROM empsalary) emp WHERE c = 1; - QUERY PLAN --------------------------------------------------------- + QUERY PLAN +------------------------------------------ WindowAgg - Run Condition: (count(empsalary.empno) OVER (?) = 1) + Run Condition: (count(1) OVER (?) = 1) -> Seq Scan on empsalary (3 rows) @@ -3763,7 +3763,7 @@ WHERE c = 1; EXPLAIN (COSTS OFF) SELECT * FROM (SELECT *, - count(salary) OVER (PARTITION BY depname || '') c1, -- w1 + count(1) OVER (PARTITION BY depname || '') c1, -- w1 row_number() OVER (PARTITION BY depname) rn, -- w2 count(*) OVER (PARTITION BY depname) c2, -- w2 count(*) OVER (PARTITION BY '' || depname) c3, -- w3 @@ -3775,7 +3775,7 @@ SELECT * FROM Subquery Scan on e -> WindowAgg Filter: (((row_number() OVER (?)) <= 1) AND ((ntile(2) OVER (?)) < 2)) - Run Condition: (count(empsalary.salary) OVER (?) <= 3) + Run Condition: (count(1) OVER (?) <= 3) -> Sort Sort Key: (((empsalary.depname)::text || ''::text)) -> WindowAgg @@ -3791,7 +3791,7 @@ SELECT * FROM -- Ensure we correctly filter out all of the run conditions from each window SELECT * FROM (SELECT *, - count(salary) OVER (PARTITION BY depname || '') c1, -- w1 + count(1) OVER (PARTITION BY depname || '') c1, -- w1 row_number() OVER (PARTITION BY depname) rn, -- w2 count(*) OVER (PARTITION BY depname) c2, -- w2 count(*) OVER (PARTITION BY '' || depname) c3, -- w3 @@ -3804,32 +3804,6 @@ SELECT * FROM sales | 3 | 4800 | 08-01-2007 | 3 | 1 | 3 | 3 | 1 (2 rows) --- Ensure we remove references to reduced outer joins as nulling rels in run --- conditions -EXPLAIN (COSTS OFF) -SELECT 1 FROM - (SELECT ntile(e2.salary) OVER (PARTITION BY e1.depname) AS c - FROM empsalary e1 LEFT JOIN empsalary e2 ON TRUE - WHERE e1.empno = e2.empno) s -WHERE s.c = 1; - QUERY PLAN ---------------------------------------------------------- - Subquery Scan on s - Filter: (s.c = 1) - -> WindowAgg - Run Condition: (ntile(e2.salary) OVER (?) <= 1) - -> Sort - Sort Key: e1.depname - -> Merge Join - Merge Cond: (e1.empno = e2.empno) - -> Sort - Sort Key: e1.empno - -> Seq Scan on empsalary e1 - -> Sort - Sort Key: e2.empno - -> Seq Scan on empsalary e2 -(14 rows) - -- Tests to ensure we don't push down the run condition when it's not valid to -- do so. -- Ensure we don't push down when the frame options show that the window @@ -3889,6 +3863,42 @@ WHERE c = 1; -> Seq Scan on empsalary (6 rows) +-- Ensure we don't use a run condition when the WindowFunc arg contains a Var +EXPLAIN (COSTS OFF) +SELECT * FROM + (SELECT empno, + salary, + count(empno) OVER (ORDER BY empno DESC) c + FROM empsalary) emp +WHERE c = 1; + QUERY PLAN +---------------------------------------------- + Subquery Scan on emp + Filter: (emp.c = 1) + -> WindowAgg + -> Sort + Sort Key: empsalary.empno DESC + -> Seq Scan on empsalary +(6 rows) + +-- As above but with ntile(). +EXPLAIN (COSTS OFF) +SELECT * FROM + (SELECT empno, + salary, + ntile(empno::int) OVER (ORDER BY empno DESC) nt + FROM empsalary) emp +WHERE nt = 1; + QUERY PLAN +---------------------------------------------- + Subquery Scan on emp + Filter: (emp.nt = 1) + -> WindowAgg + -> Sort + Sort Key: empsalary.empno DESC + -> Seq Scan on empsalary +(6 rows) + -- Ensure we don't use a run condition when the WindowFunc contains subplans EXPLAIN (COSTS OFF) SELECT * FROM diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql index c0ad51ca54..e35c16a827 100644 --- a/src/test/regress/sql/window.sql +++ b/src/test/regress/sql/window.sql @@ -1120,14 +1120,14 @@ EXPLAIN (COSTS OFF) SELECT * FROM (SELECT empno, salary, - count(empno) OVER (ORDER BY salary DESC) c + count(1) OVER (ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; SELECT * FROM (SELECT empno, salary, - count(empno) OVER (ORDER BY salary DESC) c + count(1) OVER (ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; @@ -1183,13 +1183,13 @@ SELECT empno, depname FROM FROM empsalary) emp WHERE rn < 3; --- likewise with count(empno) instead of row_number() +-- likewise with count(1) instead of row_number() EXPLAIN (COSTS OFF) SELECT * FROM (SELECT empno, depname, salary, - count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c + count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; @@ -1198,7 +1198,7 @@ SELECT * FROM (SELECT empno, depname, salary, - count(empno) OVER (PARTITION BY depname ORDER BY salary DESC) c + count(1) OVER (PARTITION BY depname ORDER BY salary DESC) c FROM empsalary) emp WHERE c <= 3; @@ -1209,7 +1209,7 @@ SELECT * FROM (SELECT empno, depname, salary, - count(empno) OVER () c + count(1) OVER () c FROM empsalary) emp WHERE c = 1; @@ -1217,7 +1217,7 @@ WHERE c = 1; EXPLAIN (COSTS OFF) SELECT * FROM (SELECT *, - count(salary) OVER (PARTITION BY depname || '') c1, -- w1 + count(1) OVER (PARTITION BY depname || '') c1, -- w1 row_number() OVER (PARTITION BY depname) rn, -- w2 count(*) OVER (PARTITION BY depname) c2, -- w2 count(*) OVER (PARTITION BY '' || depname) c3, -- w3 @@ -1228,7 +1228,7 @@ SELECT * FROM -- Ensure we correctly filter out all of the run conditions from each window SELECT * FROM (SELECT *, - count(salary) OVER (PARTITION BY depname || '') c1, -- w1 + count(1) OVER (PARTITION BY depname || '') c1, -- w1 row_number() OVER (PARTITION BY depname) rn, -- w2 count(*) OVER (PARTITION BY depname) c2, -- w2 count(*) OVER (PARTITION BY '' || depname) c3, -- w3 @@ -1236,15 +1236,6 @@ SELECT * FROM FROM empsalary ) e WHERE rn <= 1 AND c1 <= 3 AND nt < 2; --- Ensure we remove references to reduced outer joins as nulling rels in run --- conditions -EXPLAIN (COSTS OFF) -SELECT 1 FROM - (SELECT ntile(e2.salary) OVER (PARTITION BY e1.depname) AS c - FROM empsalary e1 LEFT JOIN empsalary e2 ON TRUE - WHERE e1.empno = e2.empno) s -WHERE s.c = 1; - -- Tests to ensure we don't push down the run condition when it's not valid to -- do so. @@ -1278,6 +1269,24 @@ SELECT * FROM FROM empsalary) emp WHERE c = 1; +-- Ensure we don't use a run condition when the WindowFunc arg contains a Var +EXPLAIN (COSTS OFF) +SELECT * FROM + (SELECT empno, + salary, + count(empno) OVER (ORDER BY empno DESC) c + FROM empsalary) emp +WHERE c = 1; + +-- As above but with ntile(). +EXPLAIN (COSTS OFF) +SELECT * FROM + (SELECT empno, + salary, + ntile(empno::int) OVER (ORDER BY empno DESC) nt + FROM empsalary) emp +WHERE nt = 1; + -- Ensure we don't use a run condition when the WindowFunc contains subplans EXPLAIN (COSTS OFF) SELECT * FROM