Re: Redesign per-backend statistics

Hi,

On Thu, Nov 05, 2026 at 08:17:22AM +0000, Bertrand Drouvot wrote:
> Hi,
>
> On Thu, Nov 05, 2026 at 02:19:41PM +0900, Michael Paquier wrote:
>
> > +# Verify that a statistics snapshot excludes backends that started after the
> > +# snapshot was created.
> > +my $snapshot_session = $node->background_psql($connect_db);
> >
> > Hmm. Not sure that this one is worth the cycles spent for it.
>
> This one covers a real bug that I hit while working on the re-design, so it feel
> safer for me to keep it. That said if you feel strongly about it we could get rid
> of it.

PFA the new version (I kept the above test, but I can get rid of it if you feel
strongly about it). Compared to v4, the main change is in 0002: as you suggested,
the generic infrastructure now iterates over the stats kind IDs when transferring
per-backend statistics at process exit, ProcNumber reuse and clean shutdown.

As a result, 0003-0005 no longer add direct WAL, lock and I/O accumulation calls.
0006 also renames pgstat_per_backend.c to pgstat_backend.c after removing the
existing PGSTAT_KIND_BACKEND implementation.

Also, as mentioned up-thread, support for custom per-backend statistics is left
for a follow-up.

Regards,

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