Re: tablecmds: fix bug where index rebuild loses replica identity on partitions

> On Jan 27, 2026, at 16:30, Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>
>
>
>> On Jan 27, 2026, at 15:59, Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>>
>>
>>
>>> On Jan 27, 2026, at 15:39, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>>>
>>> On Tue, Jan 27, 2026 at 01:13:32PM +0800, Chao Li wrote:
>>>> I found this bug while working on a related patch [1].
>>>>
>>>> When ALTER TABLE ... ALTER COLUMN TYPE causes an index rebuild, and
>>>> that index is used as REPLICA IDENTITY on a partitioned table, the
>>>> replica identity marking on partitions can be silently lost after the
>>>> rebuild.
>>>
>>> I am slightly confused by the tests included in the proposed patch.
>>> On HEAD, if I undo the proposed changes of tablecmds.c, the tests
>>> pass. If I run the tests of the patch with the changes of
>>> tablecmds.c, the tests also pass.
>>
>> Oops, that isn’t supposed to be so. I’ll check the test.
>>
>
> Okay, I see the problem is here:
> ```
> +CREATE UNIQUE INDEX test_replica_identity_partitioned_pkey ON test_replica_identity_partitioned (id);
> ```
>
> I missed to add column “val” into the index, so that alter type of val didn’t cause index rebuild.
>
> Ideally, it’s better to also verify that index OIDs should have changed before and after alter column type, but I haven’t figured out how to do so. Do you have an idea?

I just updated the test to store index OIDs before and after rebuild into 2 temp tables, so that we can compare the OIDs to verify rebuild happens and replica identity preserved.

I tried to port the test to master branch, and the test failed. From the test diff file, we can see replica identity lost on 3 leaf partitions:
```
@@ -360,9 +360,9 @@
ORDER BY b.index_name;
index_name | rebuilt | ri_lost
---------------------------------------------------+---------+---------
- test_replica_identity_partitioned_p1_id_val_idx | t | f
- test_replica_identity_partitioned_p2_1_id_val_idx | t | f
- test_replica_identity_partitioned_p2_2_id_val_idx | t | f
+ test_replica_identity_partitioned_p1_id_val_idx | t | t
+ test_replica_identity_partitioned_p2_1_id_val_idx | t | t
+ test_replica_identity_partitioned_p2_2_id_val_idx | t | t
test_replica_identity_partitioned_p2_id_val_idx | t | f
test_replica_identity_partitioned_pkey | t | f
(5 rows)
```

With this patch, the test passes and all replica identity are preserved.

PFA v3:
* Enhanced the test.
* A small change in find_partition_replica_identity_indexes(): if we will not update a partition, then unlock it.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/