Re: Logical Replication of sequences

On Thu, Jun 6, 2024 at 9:34 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Jun 5, 2024 at 3:17 PM Bharath Rupireddy
> <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
> >
> > On Tue, Jun 4, 2024 at 5:40 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > Even if we decode it periodically (say each time we decode the
> > > checkpoint record) then also we need to send the entire set of
> > > sequences at shutdown. This is because the sequences may have changed
> > > from the last time we sent them.
> >
> > Agree. How about decoding and sending only the sequences that are
> > changed from the last time when they were sent? I know it requires a
> > bit of tracking and more work, but all I'm looking for is to reduce
> > the amount of work that walsenders need to do during the shutdown.
> >
>
> I see your point but going towards tracking the changed sequences
> sounds like moving towards what we do for incremental backups unless
> we can invent some other smart way.

Yes, we would need an entirely new infrastructure to track the
sequence change since the last sync. We can only determine this from
WAL, and relying on it would somehow bring us back to the approach we
were trying to achieve with logical decoding of sequences patch.

> > Having said that, I like the idea of letting the user sync the
> > sequences via ALTER SUBSCRIPTION command and not weave the logic into
> > the shutdown checkpoint path. As Peter Eisentraut said here
> > https://www.postgresql.org/message-id/42e5cb35-4aeb-4f58-8091-90619c7c3ecc%40eisentraut.org,
> > this can be a good starting point to get going.
> >
>
> Agreed.

+1

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com