Re: Avoid resetting subscription two_phase state to pending when already enabled

Hi,

On Wed, Nov 4, 2026 at 6:01 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Thu, Oct 29, 2026 at 8:44 PM Zhijie Hou <houzhijie22(at)gmail(dot)com> wrote:
> >
> > On Thu, Oct 29, 2026 at 06:41 PM Bertrand Drouvot wrote:
> > > It might be worth fixing, as preserving 'e' only when slot_name is unchanged
> > > should be simple enough.
> >
> > I don't think handling that here would be simple. Resetting ENABLED to
> > PENDING when slot_name is changed would re-introduce the same bugs that
> > this patch aims to fix: prepared transactions from the previous slot may
> > still exist on the subscriber, and if the replacement slot already has
> > two_phase enabled on the publisher, prepared transactions could again be
> > streamed concurrently with table synchronization. Avoiding that would
> > require checking prepared transactions and the remote slot's status
> > during the change, which would complicate the fix.
> >
>
> I agree that we don't need to preserve the old behavior as it will
> open up other bugs and we already document that such slot's properties
> should match subscription's options. But I feel we should add that
> change in behavior for new slot's in the commit message. Other than
> that the latest patch in this thread looks good to me.

I added a section describing this behavior change, please see the
attached V3 patch.

I confirmed the patch applies cleanly to all affected branches (PG 18
through HEAD),
and the tests pass on all of them.

--
Best Regards,
Zhijie Hou