Horton

Re: Replication slot stats misgivings

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
Date: 2021-04-22T02:21:45Z
Lists: pgsql-hackers 
On Wed, Apr 21, 2021 at 4:44 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> On Tue, Apr 20, 2021 at 7:54 PM Masahiko Sawada <sawada.mshk@gmail.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/

Commits

  1. Doc: Update logical decoding stats information.

  2. Fix tests for replication slots stats.

  3. Update replication statistics after every stream/spill.

  4. Fix the computation of slot stats for 'total_bytes'.

  5. Another try to fix the test case added by commit f5fc2f5b23.

  6. Use HTAB for replication slot statistics.

  7. Fix test case added by commit f5fc2f5b23.

  8. Add information of total data processed to replication slot stats.

  9. Use NameData datatype for slotname in stats.