Our pg_stat_wal view currently doesn't expose the number of WAL segments recycled, although this information is already logged by the checkpointer in the database log. For example,
LOG: checkpoint complete: wrote 317 buffers (1.9%); 0 WAL file(s) added, 0 removed, 3 recycled; write=0.003 s, sync=0.001 s, total=0.004 s; sync files=8, longest=0.001 s, average=0.001 s; distance=56015 kB, estimate=56015 kB; lsn=0/6FB8478, redo lsn=0/6FB8420 It might be beneficial to surface the number of WAL files added, removed, and recycled in the pg_stat_wal view. As the wal_init_zero setting is typically static, I don't think it's necessary to report the number of WAL files zero-filled separately. It's important to note that the checkpoint log's count of added WAL files doesn't include files added via XLogFileInit(), which is a significant statistic to consider. What do others think? On Fri, Jan 24, 2025 at 7:22 AM Hannu Krosing <han...@google.com> wrote: > On Wed, Jan 22, 2025 at 10:18 PM Robert Pang <robertp...@google.com> > wrote: > > > > On Wed, Jan 15, 2025 at 12:05 PM Andres Freund <and...@anarazel.de> > wrote: > > > > > > If you have wal_recycle=true, this overhead will only be paid the > first time a > > > WAL segment is used, of course, not after recycling. > > > > Today, our pg_stat_wal view [1] does not report the no. of WAL > > segments recycled. How about if we add a column to report it so users > > can track how many WAL segments are recycled vs. created over a period > > of time? > > Maybe even add the full set of (recycled, created, deleted and > zero-filled) so we have a full picture. > > And possible duplicate the set for "in the background" and "inline / > stalling the production work" for the operations where it makes sense > (created, zero-filled) > > > [1] > https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW > > > > >
