Horton

Re: BUG #18988: DROP SUBSCRIPTION locks not-yet-accessed database

vignesh C <vignesh21@gmail.com>

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From: vignesh C <vignesh21@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Álvaro Herrera <alvherre@kurilemu.de>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "exclusion@gmail.com" <exclusion@gmail.com>, "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
Date: 2025-08-17T13:53:18Z
Lists: pgsql-bugs

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  1. Fix self-deadlock during DROP SUBSCRIPTION.

On Fri, 15 Aug 2025 at 11:58, Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> On Fri, Aug 15, 2025 at 11:52 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > On Thu, Aug 14, 2025 at 5:04 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > >
> > > On Thu, Aug 14, 2025 at 4:32 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > > >
> > > > On Thu, Aug 14, 2025 at 2:18 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > > > >
> > > > > On Thu, Aug 14, 2025 at 2:05 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > > > > >
> > > > > > Yeah this looks fine to me.  PFA patches for back branches.
> > > > > >
> > > > >
> > > > > Can we add a test based on the scenario reported in this email?
> > > >
> > > > At first, I thought we can just add this test in subscription.sql, but
> > > > IMHO we should not do that because after testing DROP SUBSCRIPTION
> > > > give error we should eventually DROP the subscription for cleanup by
> > > > creating the slot and enabling the subscription (as shown below[1])
> > > > but I that realized during regression wal_level is not logical so we
> > > > are not allowed to create the logical slot.  So maybe we should write
> > > > it in 100_bugs.pl?  Am I missing something?
> > > >
> > >
> > > Another alternative is for cleanup instead of creating a missing slot
> > > we can just set the slot_name=NONE and then drop. I will move ahead
> > > with this approach.
> > >
> >
> > Yeah, that sounds good to me.
> >
>
> PFA, updated patches for v13 to head, make check-world is passing for
> all the branches for v15+ we had upgrade test which also run
> regression test so we additionally have to set max_wal_senders=1 for
> 002_pg_upgrade.pl

Do you feel it will be better to append the configurations using
single call like below:
-$oldnode->append_conf('postgresql.conf', 'log_statement = none');
-$oldnode->append_conf('postgresql.conf', 'wal_level = replica');
-$oldnode->append_conf('postgresql.conf', 'max_wal_senders = 1');
+$oldnode->append_conf(
+       'postgresql.conf',
+       qq{log_statement = 'none'
+       wal_level = 'replica'
+       max_wal_senders = 1});

Regards,
Vignesh