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Fix CLUSTER tuplesorts on abbreviated expressions.

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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 <pg@bowt.ie>
Author: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/CA+hUKG+bA+bmwD36_oDxAoLrCwZjVtST2fqe=b4=qZcmU7u89A@mail.gmail.com
Backpatch: 10-
This commit is contained in:
Peter Geoghegan
2022-04-20 17:17:43 -07:00
parent eafdf9de06
commit 8ab0ebb9a8
3 changed files with 24 additions and 4 deletions
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8
src/backend/utils/sort/tuplesort.c
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@@ -1051,7 +1051,7 @@ tuplesort_begin_heap(TupleDesc tupDesc,
sortKey->ssup_nulls_first = nullsFirstFlags[i];
sortKey->ssup_attno = attNums[i];
/* Convey if abbreviation optimization is applicable in principle */
sortKey->abbreviate = (i == 0);
sortKey->abbreviate = (i == 0 && state->haveDatum1);
PrepareSortSupportFromOrderingOp(sortOperators[i], sortKey);
}
@@ -1157,7 +1157,7 @@ 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 && state->haveDatum1);
AssertState(sortKey->ssup_attno != 0);
@@ -1238,7 +1238,7 @@ tuplesort_begin_index_btree(Relation heapRel,
(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 && state->haveDatum1);
AssertState(sortKey->ssup_attno != 0);
@@ -1348,7 +1348,7 @@ tuplesort_begin_index_gist(Relation heapRel,
sortKey->ssup_nulls_first = false;
sortKey->ssup_attno = i + 1;
/* Convey if abbreviation optimization is applicable in principle */
sortKey->abbreviate = (i == 0);
sortKey->abbreviate = (i == 0 && state->haveDatum1);
AssertState(sortKey->ssup_attno != 0);