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: 2025-02-26T07:52:13Z
Lists: pgsql-hackers 
On Tue, Feb 25, 2025 at 03:00:35PM +0000, Bertrand Drouvot wrote:
> That makes fully sense. Done in 0004 attached. Somehow related to that, I've
> a patch in progress to address some of Rahila's comments ([1]) (the one related
> to the AuxiliaryPidGetProc() call is relevant specially since a051e71e28a where
> pgstat_tracks_backend_bktype() has been modified for B_WAL_RECEIVER, B_WAL_SUMMARIZER
> and B_WAL_WRITER). I'll wait for 0004 to go in before sharing the patch.

Applied v9-0001 and v9-0003 as these were fine, with more
documentation added in pgstat.h for the new WAL structure, and the 
reason why it exists.  I've noticed the difference with bktype in
v9-0004 as the WAL part does not need this information when generating
its tuple, OK here.

Doing v9-0003 after v9-0002 felt a bit odd, changing twice the
signature of pg_stat_wal_build_tuple() to adapt with the split for the
reset timestamp.

-	values[4] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp);
+	if (wal_stats.stat_reset_timestamp != 0)
+		values[4] = TimestampTzGetDatum(wal_stats.stat_reset_timestamp);
+	else
+		nulls[4] = true;

In patch v9-0002, is this nulls[4] required for the backend part?
--
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