From 5487585e376dd25d2cabc8a63a33c0286b3a199c Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: Wed, 20 Apr 2022 17:17:37 -0700 Subject: [PATCH] Fix CLUSTER tuplesorts on abbreviated expressions. CLUSTER sort won't use the datum1 SortTuple field when clustering against an index whose leading key is an expression. This makes it unsafe to use the abbreviated keys optimization, which was missed by the logic that sets up SortSupport state. Affected tuplesorts output tuples in a completely bogus order as a result (the wrong SortSupport based comparator was used for the leading attribute). This issue is similar to the bug fixed on the master branch by recent commit cc58eecc5d. But it's a far older issue, that dates back to the introduction of the abbreviated keys optimization by commit 4ea51cdfe8. Backpatch to all supported versions. Author: Peter Geoghegan Author: Thomas Munro Discussion: https://postgr.es/m/CA+hUKG+bA+bmwD36_oDxAoLrCwZjVtST2fqe=b4=qZcmU7u89A@mail.gmail.com Backpatch: 10- --- src/backend/utils/sort/tuplesort.c | 4 +++- src/test/regress/expected/cluster.out | 14 ++++++++++++++ src/test/regress/sql/cluster.sql | 6 ++++++ 3 files changed, 23 insertions(+), 1 deletion(-) diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c index f975d24a98..043d01f7d6 100644 --- a/src/backend/utils/sort/tuplesort.c +++ b/src/backend/utils/sort/tuplesort.c @@ -884,6 +884,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc, { Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate, randomAccess); + AttrNumber leading; BTScanInsert indexScanKey; MemoryContext oldcontext; int i; @@ -916,6 +917,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc, state->abbrevNext = 10; state->indexInfo = BuildIndexInfo(indexRel); + leading = state->indexInfo->ii_IndexAttrNumbers[0]; state->tupDesc = tupDesc; /* assume we need not copy tupDesc */ @@ -954,7 +956,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc, (scanKey->sk_flags & SK_BT_NULLS_FIRST) != 0; sortKey->ssup_attno = scanKey->sk_attno; /* Convey if abbreviation optimization is applicable in principle */ - sortKey->abbreviate = (i == 0); + sortKey->abbreviate = (i == 0 && leading != 0); AssertState(sortKey->ssup_attno != 0); diff --git a/src/test/regress/expected/cluster.out b/src/test/regress/expected/cluster.out index bdae8fe00c..344bab5dc0 100644 --- a/src/test/regress/expected/cluster.out +++ b/src/test/regress/expected/cluster.out @@ -506,6 +506,13 @@ SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b; COMMIT; -- and after clustering on clstr_expression_minus_a CLUSTER clstr_expression USING clstr_expression_minus_a; +WITH rows AS + (SELECT ctid, lag(a) OVER (ORDER BY ctid) AS la, a FROM clstr_expression) +SELECT * FROM rows WHERE la < a; + ctid | la | a +------+----+--- +(0 rows) + BEGIN; SET LOCAL enable_seqscan = false; EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3'; @@ -540,6 +547,13 @@ SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b; COMMIT; -- and after clustering on clstr_expression_upper_b CLUSTER clstr_expression USING clstr_expression_upper_b; +WITH rows AS + (SELECT ctid, lag(b) OVER (ORDER BY ctid) AS lb, b FROM clstr_expression) +SELECT * FROM rows WHERE upper(lb) > upper(b); + ctid | lb | b +------+----+--- +(0 rows) + BEGIN; SET LOCAL enable_seqscan = false; EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3'; diff --git a/src/test/regress/sql/cluster.sql b/src/test/regress/sql/cluster.sql index 188183647c..29ca9835ed 100644 --- a/src/test/regress/sql/cluster.sql +++ b/src/test/regress/sql/cluster.sql @@ -239,6 +239,9 @@ COMMIT; -- and after clustering on clstr_expression_minus_a CLUSTER clstr_expression USING clstr_expression_minus_a; +WITH rows AS + (SELECT ctid, lag(a) OVER (ORDER BY ctid) AS la, a FROM clstr_expression) +SELECT * FROM rows WHERE la < a; BEGIN; SET LOCAL enable_seqscan = false; EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3'; @@ -249,6 +252,9 @@ COMMIT; -- and after clustering on clstr_expression_upper_b CLUSTER clstr_expression USING clstr_expression_upper_b; +WITH rows AS + (SELECT ctid, lag(b) OVER (ORDER BY ctid) AS lb, b FROM clstr_expression) +SELECT * FROM rows WHERE upper(lb) > upper(b); BEGIN; SET LOCAL enable_seqscan = false; EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3';