Re: Re-read subscription state after lock in AlterSubscription

Hi,

On Sat, Jul 04, 2026 at 01:30:08PM +0530, Dilip Kumar wrote:
> On Fri, Jul 3, 2026 at 9:09 PM Bertrand Drouvot
> <bertranddrouvot.pg@gmail.com> wrote:
> >
> > But while doing this and looking closely, I'm not sure AlterPublication() does
> > it right. Indeed, in theory, the OID could have been re-used too (between the
> > time we did the name resolution and the time we lock the publication). I think
> > what is needed is something similar to RangeVarGetRelidExtended(), means do the
> > name resolution, acl check (ownership) and lock acquisition, all in unison.
> >
> > That's what 0003 is trying to achieve for the subscription and 0004 for the
> > publication.
> >
> > What do you think?
> >
> 0003:
> 
> It looks like the implementation of DROP SUBSCRIPTION IF EXISTS has a
> concurrent drop race condition in DropSubscription(). Currently, if
> stmt->missing_ok is true, the initial lookup safely handles a missing
> subscription. However, once a subscription is found and the code
> enters the drop loop, a second internal lookup/refetch happens. If a
> concurrent transaction drops the subscription after our initial check
> but before this internal refetch, the code throws an error.
> Essentially, the loop completely ignores the missing_ok flag during
> the refetch phase.

Good catch, will fix, thanks! 

Regards,

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