Re: LISTEN/NOTIFY bug: VACUUM sets frozenxid past a xid in async queue

Hi,

On Wed, Sep 24, 2025 at 4:59 PM Arseniy Mukhin
<arseniy(dot)mukhin(dot)dev(at)gmail(dot)com> wrote:
>
> On Wed, Sep 24, 2025 at 1:40 AM Matheus Alcantara
> <matheusssilv97(at)gmail(dot)com> wrote:
> > ...
> > > This way the listener reads the head that includes all writer's
> > > notifications and a snapshot where the writer is not in progress, so
> > > nothing stops the listener from sending these notifications and it's
> > > even possible to have the listener's position that is after the queue
> > > head, so yes, it's bad :( Sorry about that.
> > >
> > Yeah, this is bad. I'm wondering if we could reproduce such race
> > conditions scenarios with some TAP tests.
> >
>
> I agree it would be great to have more tests for such cases. As for
> the 'committed field' patch, I think we can add a TAP test that shows
> that listeners postpone processing of notifications until
> notifications were marked as 'committed=false' in case of aborted
> transactions. I tried to write one, but have not succeeded yet. Hope
> to finish it soon.

I finally managed to write a TAP test for it, so there is a new
version with the tap test.

I also realized that we can increase test coverage in
002_aborted_tx_notifies.pl if notifications of the aborted transaction
span several pages. This way we can better test
asyncQueueRollbackNotifications(). So I changed
002_aborted_tx_notifies.pl TAP test a bit.

And there is a small indentation change in lmgr.h that should fix this
git am warning.

I added all changes as a separate patch file (0002) so it was more
clear what changed. Please feel free to merge into the main patch file
/ drop any part of it that makes sense to you.

Best regards,
Arseniy Mukhin