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Commit5487585

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Fix CLUSTER tuplesorts on abbreviated expressions.
CLUSTER sort won't use the datum1 SortTuple field when clusteringagainst an index whose leading key is an expression. This makes itunsafe to use the abbreviated keys optimization, which was missed by thelogic that sets up SortSupport state. Affected tuplesorts output tuplesin a completely bogus order as a result (the wrong SortSupport basedcomparator was used for the leading attribute).This issue is similar to the bug fixed on the master branch by recentcommitcc58eec. But it's a far older issue, that dates back to theintroduction of the abbreviated keys optimization by commit4ea51cd.Backpatch to all supported versions.Author: Peter Geoghegan <pg@bowt.ie>Author: Thomas Munro <thomas.munro@gmail.com>Discussion:https://postgr.es/m/CA+hUKG+bA+bmwD36_oDxAoLrCwZjVtST2fqe=b4=qZcmU7u89A@mail.gmail.comBackpatch: 10-
1 parent33fe55c commit5487585

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3 files changed

+23
-1
lines changed

3 files changed

+23
-1
lines changed

‎src/backend/utils/sort/tuplesort.c

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -884,6 +884,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc,
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{
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Tuplesortstate*state=tuplesort_begin_common(workMem,coordinate,
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randomAccess);
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AttrNumberleading;
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BTScanInsertindexScanKey;
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MemoryContextoldcontext;
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inti;
@@ -916,6 +917,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc,
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state->abbrevNext=10;
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state->indexInfo=BuildIndexInfo(indexRel);
920+
leading=state->indexInfo->ii_IndexAttrNumbers[0];
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state->tupDesc=tupDesc;/* assume we need not copy tupDesc */
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@@ -954,7 +956,7 @@ tuplesort_begin_cluster(TupleDesc tupDesc,
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(scanKey->sk_flags&SK_BT_NULLS_FIRST)!=0;
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sortKey->ssup_attno=scanKey->sk_attno;
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/* Convey if abbreviation optimization is applicable in principle */
957-
sortKey->abbreviate= (i==0);
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sortKey->abbreviate= (i==0&&leading!=0);
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AssertState(sortKey->ssup_attno!=0);
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‎src/test/regress/expected/cluster.out

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -506,6 +506,13 @@ SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b;
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COMMIT;
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-- and after clustering on clstr_expression_minus_a
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CLUSTER clstr_expression USING clstr_expression_minus_a;
509+
WITH rows AS
510+
(SELECT ctid, lag(a) OVER (ORDER BY ctid) AS la, a FROM clstr_expression)
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SELECT * FROM rows WHERE la < a;
512+
ctid | la | a
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------+----+---
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(0 rows)
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BEGIN;
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SET LOCAL enable_seqscan = false;
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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;
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COMMIT;
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-- and after clustering on clstr_expression_upper_b
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CLUSTER clstr_expression USING clstr_expression_upper_b;
550+
WITH rows AS
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(SELECT ctid, lag(b) OVER (ORDER BY ctid) AS lb, b FROM clstr_expression)
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SELECT * FROM rows WHERE upper(lb) > upper(b);
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ctid | lb | b
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------+----+---
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(0 rows)
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BEGIN;
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SET LOCAL enable_seqscan = false;
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EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE upper(b) = 'PREFIX3';

‎src/test/regress/sql/cluster.sql

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -239,6 +239,9 @@ COMMIT;
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-- and after clustering on clstr_expression_minus_a
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CLUSTER clstr_expression USING clstr_expression_minus_a;
242+
WITH rowsAS
243+
(SELECT ctid, lag(a) OVER (ORDER BY ctid)AS la, aFROM clstr_expression)
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SELECT*FROM rowsWHERE la< a;
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BEGIN;
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SET LOCAL enable_seqscan= false;
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EXPLAIN (COSTS OFF)SELECT*FROM clstr_expressionWHEREupper(b)='PREFIX3';
@@ -249,6 +252,9 @@ COMMIT;
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-- and after clustering on clstr_expression_upper_b
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CLUSTER clstr_expression USING clstr_expression_upper_b;
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WITH rowsAS
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(SELECT ctid, lag(b) OVER (ORDER BY ctid)AS lb, bFROM clstr_expression)
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SELECT*FROM rowsWHEREupper(lb)>upper(b);
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BEGIN;
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SET LOCAL enable_seqscan= false;
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EXPLAIN (COSTS OFF)SELECT*FROM clstr_expressionWHEREupper(b)='PREFIX3';

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