Re: Skipping logical replication transactions on subscriber side

On Fri, Nov 19, 2021 at 12:22 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Fri, Nov 19, 2021 at 11:09 AM vignesh C <vignesh21@gmail.com> wrote:
> >
> > On Fri, Nov 19, 2021 at 9:22 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > >
> > > On Thu, Nov 18, 2021 at 5:10 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > > >
> > > > On Thu, Nov 18, 2021 at 5:45 PM tanghy.fnst@fujitsu.com
> > > > <tanghy.fnst@fujitsu.com> wrote:
> > > > >
> > > > > On Tuesday, November 16, 2021 2:31 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> > > > > >
> > > > > > Right. I've fixed this issue and attached an updated patch.
> > > > > >
> > > > > >
> > > > >
> > > > > Thanks for your patch.
> > > > >
> > > > > I read the discussion about stats entries for table sync worker[1], the
> > > > > statistics are retained after table sync worker finished its jobs and user can remove
> > > > > them via pg_stat_reset_subscription_worker function.
> > > > >
> > > > > But I notice that, if a table sync worker finished its jobs, the error reported by
> > > > > this worker will not be shown in the pg_stat_subscription_workers view. (It seemed caused by this condition:
"WHEREsrsubstate <> 'r'") Is it intentional? I think this may cause a result that users don't know the statistics are
stillexist, and won't remove the statistics manually. And that is not friendly to users' storage, right? 
> > > > >
> > > >
> > > > You're right. The condition "WHERE substate <> 'r') should be removed.
> > > > I'll do that change in the next version patch. Thanks!
> > > >
> > >
> > > One more thing you might want to consider for the next version is
> > > whether to rename the columns as discussed in the related thread [1]?
> > > I think we should consider future work and name them accordingly.
> > >
> > > [1] -
https://www.postgresql.org/message-id/CAA4eK1KR41bRUuPeNBSGv2%2Bq7ROKukS3myeAUqrZMD8MEwR0DQ%40mail.gmail.com
> >
> > Since the statistics collector process uses UDP socket, the sequencing
> > of the messages is not guaranteed. Will there be a problem if
> > Subscription is dropped and stats collector receives
> > PGSTAT_MTYPE_SUBSCRIPTIONPURGE first and the subscription worker entry
> > is removed and then receives PGSTAT_MTYPE_SUBWORKERERROR(this order
> > can happen because of UDP socket). I'm not sure if the Assert will be
> > a problem in this case.
> >
>
> Why that Assert will hit? We seem to be always passing 'create' as
> true so it should create a new entry. I think a similar situation can
> happen for functions and it will be probably cleaned in the next
> vacuum cycle.

Since we are passing true that Assert will not hit, sorry I missed to
notice that. It will create a new entry as you rightly pointed out.
Since the cleaning is handled by vacuum and current code is also doing
that way, I felt no need to make any change.

Regards,
Vignesh