Re: per backend WAL statistics

Hi,

On Mon, Feb 17, 2025 at 07:59:26AM +0000, Bertrand Drouvot wrote:
> Hi,
>
> On Mon, Feb 17, 2025 at 04:25:46PM +0900, Michael Paquier wrote:
> > On Mon, Feb 17, 2025 at 06:59:40AM +0000, Bertrand Drouvot wrote:
> > > There is still something that would simplify what is done here: it's the
> > > "the elimination of the write & sync columns for pg_stat_wal" mentioned in [2].
> >
> > Yeah, still you cannot just remove them because the data tracked in
> > pg_stat_io is not entirely the same, right?
>
> I think that we can just remove them. They are tracked and incremented at the
> exact same places in issue_xlog_fsync() and XLogWrite(). What differs is the
> "bytes" (as pg_stat_wal.wal_bytes somehow "focus" on the wal records size while
> the pg_stat_io's unit is the wal_block_size) and we keep them in both places.
> Also it looks like we can get rid of PendingWalStats...

PFA the whole picture. 0001 is implementing the fields removal in pg_stat_wal
(and also PendingWalStats). I think that's ok given the backend's type for which
pgstat_tracks_io_bktype() returns false. But now you make me doubt about 0001.
Anyway, it's probably better to move the 0001 discussion to a dedicated thread,
thoughts?

Regards,

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