RE: New statistics for tuning WAL buffer size

From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
> Another reason that I mildly want to object to subdivided functions is
> I was annoyed that a stats view makes many individual calls to
> functions that internally share the same statistics entry.  That
> behavior required me to provide an entry-caching feature to my
> shared-memory statistics patch.

+1
The views for troubleshooting performance problems should be as light as possible.  IIRC, we saw  frequently searching
pg_stat_replicationconsume unexpectedly high CPU power, because it calls pg_stat_get_activity(null) to get all sessions
andjoin them with the walsenders.  At that time, we had hundreds of client sessions.  We expected pg_stat_replication
tobe very lightweight because it provides information about a few walsenders. 


Regards
Takayuki Tsunakawa