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Disallow partitionwise join when collations don't match

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If the collation of any join key column doesn’t match the collation of
the corresponding partition key, partitionwise joins can yield incorrect
results. For example, rows that would match under the join key collation
might be located in different partitions due to the partitioning
collation. In such cases, a partitionwise join would yield different
results from a non-partitionwise join, so disallow it in such cases.

Reported-by: Tender Wang <tndrwang@gmail.com>
Author: Jian He <jian.universality@gmail.com>
Reviewed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
Discussion: https://postgr.es/m/CAHewXNno_HKiQ6PqyLYfuqDtwp7KKHZiH1J7Pqyz0nr+PS2Dwg@mail.gmail.com
Backpatch-through: 12
This commit is contained in:
Amit Langote
2024-11-08 16:27:24 +09:00
parent 90fe6251c8
commit 075acdd933
3 changed files with 324 additions and 2 deletions
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28
src/backend/optimizer/util/relnode.c
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@ -2185,6 +2185,10 @@ have_partkey_equi_join(PlannerInfo *root, RelOptInfo *joinrel,
if (pk_known_equal[ipk1])
continue;
/* Reject if the partition key collation differs from the clause's. */
if (rel1->part_scheme->partcollation[ipk1] != opexpr->inputcollid)
return false;
/*
* The clause allows partitionwise join only if it uses the same
* operator family as that specified by the partition key.
@ -2258,6 +2262,8 @@ have_partkey_equi_join(PlannerInfo *root, RelOptInfo *joinrel,
{
Node *expr1 = (Node *) lfirst(lc);
ListCell *lc2;
Oid partcoll1 = rel1->part_scheme->partcollation[ipk];
Oid exprcoll1 = exprCollation(expr1);
foreach(lc2, rel2->partexprs[ipk])
{
@ -2265,8 +2271,26 @@ have_partkey_equi_join(PlannerInfo *root, RelOptInfo *joinrel,
if (exprs_known_equal(root, expr1, expr2, btree_opfamily))
{
pk_known_equal[ipk] = true;
break;
/*
* Ensure that the collation of the expression matches
* that of the partition key. Checking just one collation
* (partcoll1 and exprcoll1) suffices because partcoll1
* and partcoll2, as well as exprcoll1 and exprcoll2,
* should be identical. This holds because both rel1 and
* rel2 use the same PartitionScheme and expr1 and expr2
* are equal.
*/
if (partcoll1 == exprcoll1)
{
Oid partcoll2 PG_USED_FOR_ASSERTS_ONLY =
rel2->part_scheme->partcollation[ipk];
Oid exprcoll2 PG_USED_FOR_ASSERTS_ONLY =
exprCollation(expr2);
Assert(partcoll2 == exprcoll2);
pk_known_equal[ipk] = true;
break;
}
}
}
if (pk_known_equal[ipk])