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Re: BUG #19100: Different column type between partitioned table and detached pending partition table make errors - Mailing list pgsql-bugs

From Haiyang Li
Subject Re: BUG #19100: Different column type between partitioned table and detached pending partition table make errors
Date
Msg-id f2bb794d-96f4-440e-93d3-e5c51fe2b6cc.mohen.lhy@alibaba-inc.com
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In response to Re: BUG #19100: Different column type between partitioned table and detached pending partition table make errors  (Tom Lane <tgl@sss.pgh.pa.us>)
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Hello,

Thanks for your opinion.

Tom Lane <tgl@sss.pgh.pa.us> 2025-11-3日 02:36 write:
>> IMO, a detach pending child table is not affected by parent's DML or DQL,
>> but should still be affected by parent's DDL.
>
>I think it'd be far safer to refuse all forms of ALTER TABLE until the
> detach is completed.

I have been trying to think of a concrete scenario where this could cause problems
if ALTER TABLE permitted on detach pending partitions.
But I haven't come up with one yet. Could you provide an example or suggest some
possible cases?

OTOH, from a safety perspective, I would argue that pg_dump should avoid emitting
ATTACH PARTITION statements for detach pending child tables.

Regards,
Haiyang Li


------------------------------------------------------------------
From:Tom Lane <tgl@sss.pgh.pa.us>
Send Time:2025年11月3日(周一) 02:36
To:"李海洋(陌痕)"<mohen.lhy@alibaba-inc.com>
CC:"pgsql-bugs"<pgsql-bugs@lists.postgresql.org>
Subject:Re: BUG #19100: Different column type between partitioned table and detached pending partition table make errors

PG Bug reporting form <noreply@postgresql.org> writes:
> It's evident that in both error cases, the failure occurs because
> column name has different data types between the parent and the child
> table. BTW, "\d+ users_p0" error happens when
> pg_get_partition_constraintdef() is called. The root cause seems to be
> that when running:
> ```
> ALTER TABLE users ALTER COLUMN name TYPE char(10);
> ```
> on the parent table, the statement does not affect a child table that is in
> detach pending state.

Ugh.

> IMO, a detach pending child table is not affected by parent's DML or DQL,
> but should still be affected by parent's DDL.

I think it'd be far safer to refuse all forms of ALTER TABLE until the
detach is completed.

  regards, tom lane

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