On Thu, 15 Feb 2024 at 08:42, Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Wed, Feb 14, 2024 at 12:58 PM vignesh C <vignesh21@gmail.com> wrote:
> >
> > On Wed, 7 Feb 2024 at 16:27, vignesh C <vignesh21@gmail.com> wrote:
> > >
> > > I was able to reproduce the issue consistently with the changes shared
> > > by Tom Lane at [1].
> > > I have made changes to change ALTER SUBSCRIPTION to DROP+CREATE
> > > SUBSCRIPTION and verified that the test has passed consistently for
> > > >50 runs that I ran. Also the test execution time increased for this
> > > case is very negligibly:
> > > Without patch: 7.991 seconds
> > > With test change patch: 8.121 seconds
> > >
> > > The test changes for the same are attached.
> >
> > Alternative, this could also be fixed like the changes proposed by
> > Amit at [1]. In this case we ignore publications that are not found
> > for the purpose of computing RelSyncEntry attributes. We won't mark
> > such an entry as valid till all the publications are loaded without
> > anything missing. This means we won't publish operations on tables
> > corresponding to that publication till we found such a publication and
> > that seems okay.
> >
> > Tomas had raised a performance issue forcing us to reload it for every
> > replicated change/row in case the publications are invalid at [2].
> >
>
> Did you measure the performance impact? I think it should impact the
> performance only when there is a dropped/non-existent publication as
> per the subscription definition.
The performance was almost similar in this case:
Without patch: 7.991 seconds
With skip_not_exist_publication option patch: 7.996 seconds
> Also, in the same email[2], Tomas
> raised another concern that in such cases it is better to break the
> replication.
I will handle this in the next version
> >
> How
> > about keeping the default option as it is and providing a new option
> > skip_not_exist_publication while creating/altering a subscription. In
> > this case if skip_not_exist_publication is specified we will ignore
> > the case if publication is not present and publications will be kept
> > in invalid and get validated later.
> >
>
> I don't know if this deserves a separate option or not but I think it
> is better to discuss this in a separate thread.
I will start a separate thread for this.
> To resolve the BF
> failure, I still feel, we should just recreate the subscription. This
> is a pre-existing problem and we can track it via a separate patch
> with a test case targetting such failures.
+1 for going with recreation of the subscription, the changes for this
are available at [1].
[1] - https://www.postgresql.org/message-id/CALDaNm1hLZW4H4Z61swK6WPW6pcNcjzXqw%3D6NqG7e-RMtkFaZA%40mail.gmail.com
Regards,
Vignesh
