Re: How can I change replication slot's restart_lsn from SQL?

On Wed, 2023-05-17 at 08:21 +0200, hubert depesz lubaczewski wrote:
> On Wed, May 17, 2023 at 08:16:41AM +0200, Laurenz Albe wrote:
> > On Tue, 2023-05-16 at 19:35 +0200, hubert depesz lubaczewski wrote:
> > > > I'm working on a workaround for a bug in Pg
> > > > (https://www.postgresql.org/message-id/flat/Yz2hivgyjS1RfMKs%40depesz.com)
> > > > I want to create replication slot, and advance is manually, keeping it
> > > > always a bit lagging behind real replication slot.
> > > >
> > > > How can I advance restart_lsn of a slot?
> > >
> > > if doing it via SQL is not an option, is there any way to have
> > > replication slot and modify it's restart_lsn, regardless of whether it
> > > will b e physical, or logical, and what tool shoudl I use.
> > >
> > > I tried with pg_recvlogical, and read
> > > https://www.postgresql.org/docs/current/protocol-replication.html but
> > > I don't see how I can make restart_lsn advance to anything.
> >
> > You could shutdown the server and edit the file in "pg_replslot" with
> > a hex editor.  Not very convenient, and you'd have to study the source
> > to understand the format of the file.
>
> OK. Shutting down production server every 5 minutes to advance the slot
> isn't really an option.
>
> How do "normal" wal consumers update restart_lsn? Is there a reason why
> it can't be done using pg_rec(eive|v)* ?

I thought that was a one-time operation. No idea if there are alternatives.

Yours,
Laurenz Albe