Re: lock contention, need profiling idea

On Tue, Jul 1, 2014 at 7:36 AM, AI Rumman <rummandba@gmail.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