Re: pg_stat_activity.waiting_start

On Sat, Jan 7, 2017 at 01:25:08PM +0000, Greg Stark wrote:
> I would actually argue the reverse of the above proposal would be more
> useful. What we need are counts of how often LWLocks take longer than,
> say, 50ms and for shorter waits we need to know how long. Perhaps not
> precisely for individual waits but in aggregate we need the totals to
> be right so as long as the measurements are accurate that would be
> sufficient. So an accurate but imprecise measurement +/- 10ms with low
> overhead is better than a precise measurement with high overhead.

I agree those values are important, but I don't think people are going
to be able to use pg_stat_activity to get them, so I don't see the point
of trying to supply them there.

See
https://www.postgresql.org/message-id/CA+Tgmoav9Q5v5ZGT3+wP_1tQjT6TGYXrwrDcTRrWimC+ZY7RRA@mail.gmail.com
for an excellent example of getting those values via polling.

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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