v2-0001-Check-collation-when-creating-partitioned-index.patch

From 869a66c429eb188ceafcbd972b6e46b63fce88f3 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Thu, 23 Nov 2023 10:37:21 +0100
Subject: [PATCH v2] Check collation when creating partitioned index

When creating a partitioned index, the partition key must be a subset
of the index's columns.  But this currently doesn't check that the
collations between the partition key and the index definition match.
So you can construct a unique index that fails to enforce uniqueness.
(This would most likely involve a nondeterministic collation, so it
would have to be crafted explicitly and is not something that would
just happen by accident.)

This patch adds the required collation check.  As a result, any
previously allowed unique index that has a collation mismatch would no
longer be allowed to be created.

Discussion: https://www.postgresql.org/message-id/flat/3327cb54-f7f1-413b-8fdb-7a9dceebb938%40eisentraut.org
---
 src/backend/commands/indexcmds.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 0b3b8e98b8..c7ecedbe3b 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -1011,10 +1011,13 @@ DefineIndex(Oid tableId,
 			{
 				if (key->partattrs[i] == indexInfo->ii_IndexAttrNumbers[j])
 				{
-					/* Matched the column, now what about the equality op? */
+					/* Matched the column, now what about the collation and equality op? */
 					Oid			idx_opfamily;
 					Oid			idx_opcintype;
 
+					if (key->partcollation[i] != collationIds[j])
+						continue;
+
 					if (get_opclass_opfamily_and_input_type(opclassIds[j],
 															&idx_opfamily,
 															&idx_opcintype))
-- 
2.42.1