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