Re: min_safe_lsn column in pg_replication_slots view

On Wed, Jun 24, 2020 at 2:37 PM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
>
> On 2020/06/23 15:27, Amit Kapila wrote:
> >
> > Having a separate function for this seems like a good idea but can we
> > consider displaying it in a view like pg_stat_replication_slots as we
> > are discussing a nearby thread to have such a view for other things.
> > I think ultimately this information is required to check whether some
> > slot can be invalidated or not, so having it displayed along with
> > other slot information might not be a bad idea.
>
> "the current WAL LSN - max(wal_keep_segments * 16MB, max_slot_wal_keep_size)"
> is the same value between all the replication slots. But you think it's better
> to display that same value for every slots in the view?
>
> Or you're thinking to display the difference of that LSN value and
> restart_lsn as Horiguchi-san suggested?
>

I see value in Horiguchi-San's proposal. IIUC, it will tell help
DBAs/Users to know if any particular slot will get invalidated soon.

> That diff varies each replication slot,
> so it seems ok to display it for every rows.
>

Yes.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com