Re: min_safe_lsn column in pg_replication_slots view

On Thu, Jun 18, 2020 at 11:52 AM Kyotaro Horiguchi
<horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> At Wed, 17 Jun 2020 21:37:55 +0900, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote in
> > On 2020/06/15 16:35, Kyotaro Horiguchi wrote:
> > Isn't it better to use 1 as the second argument of the above,
> > in order to address the issue that I reported upthread?
> > Otherwise, the WAL file name that pg_walfile_name(min_safe_lsn)
> > returns
> > would be confusing.
>
> Mmm. pg_walfile_name seems too specialize to
> pg_stop_backup(). (pg_walfile_name_offset() returns wrong result for
> segment boundaries.) I'm not willing to do that only to follow such
> suspicious(?) specification, but surely it would practically be better
> doing that. Please find the attached first patch.
>

It is a little unclear to me how this or any proposed patch will solve
the original problem reported by Fujii-San? Basically, the problem
arises because we don't have an interlock between when the checkpoint
removes the WAL segment and the view tries to acquire the same. Am, I
missing something?

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