Re: lock contention, need profiling idea

On Tue, Jul 1, 2014 at 7:36 AM, AI Rumman <rummandba(at)gmail(dot)com> wrote:

> I see lots of similar log message at a certain time in a day on Postgresql
> 9,.1:
>
> LOG: process 18855 still waiting for ShareLock on transaction 2856146023
> after 1001.209 ms
> STATEMENT: UPDATE table1 SET time = $1 WHERE id = $2
>
> The table1 size is 17 G.
>
> What could be the reason for this lock contention?
> autovacuum?
>
This may be a CREATE INDEX query taking some time, perhaps combined with an
old prepared transaction still holding a lock? Perhaps a cron job running
behind that you are not aware of?
You should have a look at pg_stat_activity, pg_prepared_xacts and pg_locks
to get more information about the transactions running and the locks being
taken.
--
Michael