From: | David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> |
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To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: recently and selectively slow, but very simple, update query.... |
Date: | 2014-05-05 21:51:21 |
Message-ID: | 1399326680993-5802555.post@n5.nabble.com |
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Lists: | pgsql-performance |
Stelios Mavromichalis wrote
>> the load of the machine is also low (like 0.2).
Which means little if the update is waiting for a lock to be released by one
other process; which is more likely the situation (or some other concurrency
contention) especially as you said that this particular user generates
significant transaction/query volume (implied by the fact the user has the
most balance updates).
During slow-update executions you want to look at:
pg_stat_activity
pg_locks
to see what other concurrent activity is taking place.
It is doubtful that dump/restore would have any effect given that the
symptoms are sporadic and we are only talking about a select statement that
returns a single row; and an update that does not hit any indexed column and
therefore benefits from "HOT" optimization.
HTH
David J.
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