Re: speed up a logical replica setup

On Wed, 3 Jan 2024 at 14:49, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Jan 3, 2024 at 12:09 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> >
> > On Wed, 1 Nov 2023 at 19:28, Ashutosh Bapat
> > <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
> > >
> > > At this stage the standby would have various replication objects like
> > > publications, subscriptions, origins inherited from the upstream
> > > server and possibly very much active. With failover slots, it might
> > > inherit replication slots. Is it intended that the new subscriber also
> > > acts as publisher for source's subscribers OR that the new subscriber
> > > should subscribe to the upstreams of the source? Some use cases like
> > > logical standby might require that but a multi-master multi-node setup
> > > may not. The behaviour should be user configurable.
> >
> > How about we do like this:
> > a) Starting the server in binary upgrade mode(so that the existing
> > subscriptions will not try to connect to the publishers)
> >
>
> Can't we simply do it by starting the server with
> max_logical_replication_workers = 0 or is there some other need to
> start in binary upgrade mode?

I agree, max_logical_replication_workers = 0 is enough for our case.

> b) Disable
> > the subscriptions
> >
>
> Why not simply drop the subscriptions?

Dropping subscriptions is ok as these subscriptions will not be required.

> c) Drop the replication slots d) Drop the
> > publications
> >
>
> I am not so sure about dropping publications because, unlike
> subscriptions which can start to pull the data, there is no harm with
> publications. Similar to publications there could be some user-defined
> functions or other other objects which may not be required once the
> standby replica is converted to subscriber. I guess we need to leave
> those to the user.

Yes, that makes sense.

Regards,
Vignesh