Re: Replication slot stats misgivings

On Wed, Apr 21, 2021 at 4:44 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Tue, Apr 20, 2021 at 7:54 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> >
> > I've attached the patch. In addition to the test Vignesh prepared, I
> > added one test for the message for creating a slot that checks if the
> > statistics are initialized after re-creating the same name slot.
> > Please review it.
>
> Overall the patch looks good to me. However, I have one question, I
> did not understand the reason behind moving the below code from
> "pgstat_reset_replslot_counter" to "pg_stat_reset_replication_slot"?

Andres pointed out that pgstat_reset_replslot_counter() acquires lwlock[1]:

---
- pgstat_reset_replslot_counter() acquires ReplicationSlotControlLock. I
think pgstat.c has absolutely no business doing things on that level.
---

I changed the code so that pgstat_reset_replslot_counter() doesn't
acquire directly lwlock but I think that it's appropriate to do the
existence check for slots in pgstatfunc.c rather than pgstat.c.

Regards,

[1] https://www.postgresql.org/message-id/20210319185247.ldebgpdaxsowiflw%40alap3.anarazel.de

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/