On Mon, Aug 11, 2014 at 10:48 AM, Tatsuo Ishii <is...@postgresql.org> wrote: >> On Mon, Aug 11, 2014 at 9:23 AM, Tatsuo Ishii <is...@postgresql.org> wrote: >>> We can know the LSN of last committed WAL record on primary by using >>> pg_current_xlog_location(). It seems there's no API to know the time >>> when the WAL record was created. I would like to know standby delay by >>> using pg_last_xact_replay_timestamp() and such that API. >>> >>> If there's no such a API, it would be useful to invent usch an API IMO. >> >> +1 >> >> I proposed that function before, but unfortunately it failed to be applied. >> But I still think that function is useful to calculate the replication delay. >> The past discussion is >> http://www.postgresql.org/message-id/cahgqgwf3zjfunej5ka683ku5rqubtswtqfq7g1x0g34o+jx...@mail.gmail.com > > I looked into the thread briefly and found Simon and Robert gave -1 > for this because of performance concern. I'm not sure if it's a actual > performance penalty or not. Maybe we need to major the penalty?
I think that the performance penalty is negligible small because the patch I posted before added only three stores to shared memory per commit/abort. No time-consuming operations like lock, gettimeofday, etc were added. Of course, it's worth checking whether the penalty is actually small or not, though. Regards, -- Fujii Masao -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
