Re: proposal for 9.5: monitoring lock time for slow queries

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От Pavel Stehule
Тема Re: proposal for 9.5: monitoring lock time for slow queries
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Msg-id CAFj8pRAhQ-GZMABGOqU5VtxMcrVR8EEJojEMD_fhTSg3uciK7g@mail.gmail.com
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Ответ на Re: proposal for 9.5: monitoring lock time for slow queries  (Michael Paquier <michael.paquier@gmail.com>)
Ответы Re: proposal for 9.5: monitoring lock time for slow queries  ("MauMau" <maumau307@gmail.com>)
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Hi


2014-08-13 6:18 GMT+02:00 Michael Paquier <michael.paquier@gmail.com>:
On Wed, Aug 13, 2014 at 4:59 AM, Pavel Stehule <pavel.stehule@gmail.com> wrote:
> Any idea how to show a lock time in some practical form together with logged
> slow query?

Doing a join on pg_stat_activity and pg_locks is not going to help
much as you could only get the moment when query has started or its
state has changed. Have you thought about the addition of a new column
in pg_locks containing the timestamp of the moment a lock has been
taken? I am sure that we are concerned about the performance impact
that extra calls to gettimeofday could have though...
Regards,

There are two relative independent tasks

a) monitor and show total lock time of living queries

b) monitor and log total lock time of executed queries.

I am interested by @b now. When we work with slow query log, then we would to identify reason for long duration. Locks are important source of these queries on some systems.

What I know, we do monitoring these times for deadlock identification trigger and for log_lock_waits - so there should not be any new pressure to performance.

Regards

Pavel
 
--
Michael

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