Re: sequencesync worker race with REFRESH SEQUENCES

On Tue, Jul 28, 2026 at 4:14 PM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
>
> One minor comment:
> ```
> + /*
> + * Lock the sequence so its identity (namespace and name) cannot change
> + * under us via a concurrent DROP, RENAME or SET SCHEMA. Release it
> + * right away rather than at transaction end, to avoid accumulating a
> + * lock per sequence.
> + */
> + sequence_rel = try_table_open(subrel->srrelid, AccessShareLock);
> ```
>
> I think this comment is not enough. We can describe why the releasing the lock
> immediately is OK. IIUC, it's because the name and the namespace would be checked
> again in copy_sequences(), right?
>

Yes, that is correct. How about a comment as follows:
/*
* Lock the sequence so its identity (namespace and name) cannot change
* under us via a concurrent DROP, RENAME or SET SCHEMA while we read it.
* The lock is released immediately rather than at transaction end. The
* later synchronization does not depend on this captured identity
* remaining valid, as it re-opens the sequence and tolerates concurrent
* changes. Releasing early also avoids holding one lock per sequence,
* which could exhaust the lock table.
*/

--
With Regards,
Amit Kapila.