From f6974dacc76c1372eb80f46b8f5d52e8579887cd Mon Sep 17 00:00:00 2001 From: David Rowley Date: Thu, 19 Dec 2024 10:39:10 +1300 Subject: [PATCH v1] Fix Assert failure in WITH RECURSIVE UNION queries If the non-recursive part of a recursive CTE ended up using TTSOpsBufferHeapTuple as the table slot type, then a duplicate value could cause an Assert failure in CheckOpSlotCompatibility() when checking the hash table for the duplicate value. The expected slot type for the deform step was TTSOpsMinimalTuple so the Assert failed when the TTSOpsBufferHeapTuple slot was used. This is a long-standing bug which we likely didn't notice because it seems much more likely that the non-recursive term would have required projection and used a TTSOpsVirtual slot, which CheckOpSlotCompatibility is ok with. There doesn't seem to be any harm done here other than the Assert failure. Both TTSOpsMinimalTuple and TTSOpsBufferHeapTuple slot types require tuple deformation, so the EEOP_*_FETCHSOME ExprState step would have properly existed in the ExprState. The solution is to pass NULL for the ExecBuildGroupingEqual's 'lops' parameter. This means the ExprState's EEOP_*_FETCHSOME step won't expect a fixed slot type. This makes CheckOpSlotCompatibility() happy as no checking is performed when the ExprEvalStep is not expecting a fixed slot type. Reported-by: Richard Guo Discussion: https://postgr.es/m/CAMbWs4-8U9q2LAtf8+ghV11zeUReA3AmrYkxzBEv0vKnDxwkKA@mail.gmail.com Backpatch-through: 13, all supported versions --- src/backend/executor/execGrouping.c | 3 +-- src/test/regress/expected/with.out | 15 +++++++++++++++ src/test/regress/sql/with.sql | 12 ++++++++++++ 3 files changed, 28 insertions(+), 2 deletions(-) diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c index 4a8f72305c..a69fa0f8cc 100644 --- a/src/backend/executor/execGrouping.c +++ b/src/backend/executor/execGrouping.c @@ -236,9 +236,8 @@ BuildTupleHashTableExt(PlanState *parent, hash_iv); /* build comparator for all columns */ - /* XXX: should we support non-minimal tuples for the inputslot? */ hashtable->tab_eq_func = ExecBuildGroupingEqual(inputDesc, inputDesc, - &TTSOpsMinimalTuple, &TTSOpsMinimalTuple, + NULL, &TTSOpsMinimalTuple, numCols, keyColIdx, eqfuncoids, collations, allow_jit ? parent : NULL); diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out index ff9754603b..7a51e2eb75 100644 --- a/src/test/regress/expected/with.out +++ b/src/test/regress/expected/with.out @@ -656,6 +656,21 @@ SELECT t1.id, t2.path, t2 FROM t AS t1 JOIN t AS t2 ON 16 | {3,7,11,16} | (16,"{3,7,11,16}") (16 rows) +CREATE TEMP TABLE duplicates (a INT NOT NULL); +INSERT INTO duplicates VALUES(1), (1); +-- Try out a recursive UNION case where the non-recursive part's table slot +-- uses TTSOpsBufferHeapTuple and contains duplicate rows. +WITH RECURSIVE cte (a) as ( + SELECT a FROM duplicates + UNION + SELECT a FROM cte +) +SELECT a FROM cte; + a +--- + 1 +(1 row) + -- test that column statistics from a materialized CTE are available -- to upper planner (otherwise, we'd get a stupider plan) explain (costs off) diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql index aca7bae6dd..dcdaab5eff 100644 --- a/src/test/regress/sql/with.sql +++ b/src/test/regress/sql/with.sql @@ -361,6 +361,18 @@ UNION ALL SELECT t1.id, t2.path, t2 FROM t AS t1 JOIN t AS t2 ON (t1.id=t2.id); +CREATE TEMP TABLE duplicates (a INT NOT NULL); +INSERT INTO duplicates VALUES(1), (1); + +-- Try out a recursive UNION case where the non-recursive part's table slot +-- uses TTSOpsBufferHeapTuple and contains duplicate rows. +WITH RECURSIVE cte (a) as ( + SELECT a FROM duplicates + UNION + SELECT a FROM cte +) +SELECT a FROM cte; + -- test that column statistics from a materialized CTE are available -- to upper planner (otherwise, we'd get a stupider plan) explain (costs off) -- 2.34.1