Re: Lost replication slots after pg_upgrade.

Hi Julien,

Thank you for the information. I wanted to understand why the replication
slot is removed after or during upgrade?

Thanks,
Nikhil

On Tue, Feb 8, 2022 at 12:34 PM Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:

> Hi,
>
> On Tue, Feb 08, 2022 at 12:24:56PM +0530, Nikhil Shetty wrote:
> >
> > I am doing a major version upgrade from pg 11 to 13. The point is if I
> lose
> > the replication slot after upgrade then how will I sync standby from
> > primary after rsync.
> >
> > I can create the slot after upgrading but won't there be dataloss?
>
> The replication slots are only there to make sure that the primary server
> won't
> remove needed WALs before the standby can retrieve them. Unless you start
> production activity just after the pg_upgrade and before finishing
> rebuilding
> the secondary there shouldn't be enough activity to lead to removing old
> WALs.
> But if you do, you can create the needed replication slot(s) manually just
> after the pg_upgrade. But as already mentioned, I also recommend using
> pg_basebackup for rebuilding the standby server(s).
>
> > pg_basebackup takes time for large databases (> 5TB). I feel rsync should
> > be faster.
>
> Not necessarily. pg_basebackup will do simple sequential read of all the
> data,
> which is probably the fastest thing to do. rsync will do some extra
> processing
> that isn't required in that scenario, so it's likely to be slower (although
> probably only marginally slower).
>