Re: Logical Replication of sequences

On Mon, Jun 10, 2024 at 5:00 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:

> On Mon, 10 Jun 2024 at 12:24, Amul Sul <sulamul(at)gmail(dot)com> wrote:
> >
> >
> >
> > On Sat, Jun 8, 2024 at 6:43 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> >>
> >> On Wed, 5 Jun 2024 at 14:11, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> wrote:
> >> [...]
> >> A new catalog table, pg_subscription_seq, has been introduced for
> >> mapping subscriptions to sequences. Additionally, the sequence LSN
> >> (Log Sequence Number) is stored, facilitating determination of
> >> sequence changes occurring before or after the returned sequence
> >> state.
> >
> >
> > Can't it be done using pg_depend? It seems a bit excessive unless I'm
> missing
> > something.
>
> We'll require the lsn because the sequence LSN informs the user that
> it has been synchronized up to the LSN in pg_subscription_seq. Since
> we are not supporting incremental sync, the user will be able to
> identify if he should run refresh sequences or not by checking the lsn
> of the pg_subscription_seq and the lsn of the sequence(using
> pg_sequence_state added) in the publisher. Also, this parallels our
> implementation for pg_subscription_seq and will aid in expanding for
> a) incremental synchronization and b) utilizing workers for
> synchronization using sequence states if necessary.
>
> How do you track sequence mapping with the publication?
>
> In the publisher we use pg_publication_rel and
> pg_publication_namespace for mapping the sequences with the
> publication.
>

Thanks for the explanation. I'm wondering what the complexity would be, if
we
wanted to do something similar on the subscriber side, i.e., tracking via
pg_subscription_rel.

Regards,
Amul