Re: min_safe_lsn column in pg_replication_slots view

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: min_safe_lsn column in pg_replication_slots view
Date: 2020-06-22 12:01:16
Message-ID: CAA4eK1JBGLnSxaY4xEjDSDZBtTgWmbxA3YfknEZj3cfE5zu51w@mail.gmail.com
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On Mon, Jun 22, 2020 at 11:19 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Sat, Jun 20, 2020 at 03:53:54PM +0900, Michael Paquier wrote:
> > On Sat, Jun 20, 2020 at 09:45:52AM +0530, Amit Kapila wrote:
> >> Isn't this information specific to checkpoints, so maybe better to
> >> display in view pg_stat_bgwriter?
> >
> > Not sure that's a good match. If we decide to expose that, a separate
> > function returning a LSN based on the segment number from
> > XLogGetLastRemovedSegno() sounds fine to me, like
> > pg_wal_last_recycled_lsn(). Perhaps somebody has a better name in
> > mind?
>
> I was thinking on this one for the last couple of days, and came up
> with the name pg_wal_oldest_lsn(), as per the attached, traking the
> oldest WAL location still available.
>

I feel such a function is good to have but I am not sure if there is a
need to tie it with the removal of min_safe_lsn column.

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

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