Date: Fri, 3 Jul 2026 04:19:00 +0000
From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>,
	'Dilip Kumar' <dilipbalaut@gmail.com>
Subject: Re: Re-read subscription state after lock in AlterSubscription
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Hi Kuroda-san,

On Fri, Jul 03, 2026 at 03:13:08AM +0000, Hayato Kuroda (Fujitsu) wrote:
> Dear Bertrand,
> 
> > Yeah, but I think they would produce "tuple concurrently updated" error (due to
> > CatalogTupleUpdate) so that invalid information could not be used.
> 
> I confirmed with PG14 that tuple concurrently updated ERROR can be raised when
> ALTER SUBSCRIPTION DISABLE happens concurrently:
> 
> ```
> postgres=# ALTER SUBSCRIPTION sub DISABLE ;
> ERROR:  tuple concurrently updated
> ```

Yeah, reproducible by using a breakpoint just before acquiring the lock for example.

> It might be harmless but I think the correct ERROR should be reported: the patch
> should be backpatched. Thought?

I'm not sure about the back patch part as it would only improve error messages
in a rare race condition (and there is no risk of invalid data being used).

Since a5918fddf10, that's a different story because a table creation is now
involved.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com