From 7b8d45d278de62b23777b36e1515c34d2eaeaf66 Mon Sep 17 00:00:00 2001 From: David Rowley Date: Thu, 19 Dec 2024 13:12:18 +1300 Subject: [PATCH] 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 Reviewed-by: Tom Lane 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 7233f1e3c03..7f6d7703b4c 100644 --- a/src/backend/executor/execGrouping.c +++ b/src/backend/executor/execGrouping.c @@ -224,9 +224,8 @@ BuildTupleHashTableExt(PlanState *parent, allow_jit = metacxt != tablecxt; /* 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 08cfa5463fb..460d0ea2b1c 100644 --- a/src/test/regress/expected/with.out +++ b/src/test/regress/expected/with.out @@ -636,6 +636,21 @@ 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 8f6e6c0b405..bcf0242fa40 100644 --- a/src/test/regress/sql/with.sql +++ b/src/test/regress/sql/with.sql @@ -347,6 +347,18 @@ 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)