Hi, On Wed, 8 Nov 2023 at 04:19, Andres Freund <and...@anarazel.de> wrote: > > Hi, > > On 2023-11-08 09:52:16 +0900, Michael Paquier wrote: > > By the way, if the write/sync quantities and times begin to be tracked > > by pg_stat_io, I'd see a pretty good argument in removing the > > equivalent columns in pg_stat_wal. It looks like this would reduce > > the confusion related to the handling of PendingWalStats added in > > pgstat_io.c, for one. > > Another approach would be to fetch the relevant columns from pg_stat_io in the > pg_stat_wal view. That'd avoid double accounting and breaking existing > monitoring.
There are some differences between pg_stat_wal and pg_stat_io while collecting WAL stats. For example in the XLogWrite() function in the xlog.c file, pg_stat_wal counts wal_writes as write system calls. This is not something we want for pg_stat_io since pg_stat_io counts the number of blocks rather than the system calls, so instead incremented pg_stat_io by npages. Could that cause a problem since pg_stat_wal's behaviour will be changed? Of course, as an alternative we could change pg_stat_io's behaviour but in the end either pg_stat_wal's or pg_stat_io's behaviour will be changed. Regards, Nazir Bilal Yavuz Microsoft