Re: Show WAL write and fsync stats in pg_stat_io

Hi,

On Fri, Jan 24, 2025 at 11:31:02AM +0300, Nazir Bilal Yavuz wrote:
> v9 is rebased and attached as three patches. The first one is a
> squashed patch for the current version of Andres' proposed fix to pass
> the CI, the second one is for adding WAL stats to pg_stat_io and the
> third one is for fetching timing columns from pg_stat_io in the
> pg_stat_wal view.

Thanks for the patch!

I did not look at the code yet but did a few tests.
I can see diff between pg_stat_wal and pg_stat_io, for example:

"
postgres=# select pg_stat_reset_shared();
pg_stat_reset_shared
----------------------

(1 row)

postgres=# insert into bdt select a from generate_series(1,200000) a ;
INSERT 0 200000

postgres=# select wal_bytes,stats_reset from pg_stat_wal;
wal_bytes | stats_reset
-----------+-------------------------------
11800088 | 2025-01-24 14:17:28.507994+00
(1 row)

postgres=# select sum(write_bytes),stats_reset from pg_stat_io where object = 'wal' group by stats_reset;
sum | stats_reset
----------+-------------------------------
12853248 | 2025-01-24 14:17:28.507988+00
(1 row)

Is that expected?

Regards,

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