Horton

Re: per backend WAL statistics

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org, Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: 2025-02-28T02:34:14Z
Lists: pgsql-hackers

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On Thu, Feb 27, 2025 at 07:47:09AM +0000, Bertrand Drouvot wrote:
> That's how I did it initially but decided to move it to pgstat_backend.c. The
> reason was that it's fully linked to "per backend" stats and that there is
> no SQL api on top of it (while I think that's the case for almost all the ones
> in pgstatfuncs.c). Thoughts?

Okay by me with pgstat_fetch_stat_backend in parallel, why not
exposing this part as well..  Perhaps that could be useful for some
extension?  I'd rather have out-of-core code do these lookups with the
same sanity checks in place for the procnumber and slot lookups.

The name was inconsistent with the rest of the file, so I have settled
to a pgstat_fetch_stat_backend_by_pid() to be more consistent.  A
second thing is to properly initialize bktype if defined by the
caller.

> Makes sense. I did not had in mind to submit a new patch version (to at least
> implement the above) without getting your final thoughts on your first comment.
> But since a rebase is needed anyway,then please find attached a new version. It
> just implements your last comment.

Attached is a rebased version of the rest.
--
Michael

Commits

  1. Fix use-after-free in pgstat_fetch_stat_backend_by_pid()

  2. Remove initialization from PendingBackendStats

  3. Add WAL data to backend statistics

  4. Improve check for detection of pending data in backend statistics

  5. Fix some gaps in pg_stat_io with WAL receiver and WAL summarizer

  6. Handle auxiliary processes in SQL functions of backend statistics

  7. Invent pgstat_fetch_stat_backend_by_pid()

  8. Refactor code of pg_stat_get_wal() building result tuple

  9. Adding new PgStat_WalCounters structure in pgstat.h

  10. Remove pgstat_flush_wal()

  11. Refactor some code related to backend statistics

  12. Add backend-level statistics to pgstats