Horton

Re: per backend WAL statistics

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

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From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org, Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: 2025-02-27T07:47:09Z
Lists: pgsql-hackers

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Hi,

On Thu, Feb 27, 2025 at 12:02:51PM +0900, Michael Paquier wrote:
> 0001 was OK, so done.

Thanks!

> In 0002, couldn't it be better to have the pg_stat_get_backend_stats()
> static in pgstatfuncs.c?  In 0003, pg_stat_get_backend_wal() is also
> in pgstatfuncs.c, meaning that all the callers of
> pg_stat_get_backend_stats() would be in this file.

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?

> -typedef struct PgStat_Backend
> -{
> -	TimestampTz stat_reset_timestamp;
> -	PgStat_BktypeIO io_stats;
> -} PgStat_Backend;
> -
>  /* ---------
>   * PgStat_BackendPending	Non-flushed backend stats.
>   * ---------
> 
> In 0003, let's keep PgStat_BackendPending grouped with PgStat_Backend,
> so it sounds better to move both of them after the WAL stats
> structures.

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.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

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