From: David G Johnston <david.g.johnston@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: recently and selectively slow, but very simple, update query....
Date: Mon, 5 May 2014 14:51:21 -0700 (PDT)
Message-ID: <1399326680993-5802555.post@n5.nabble.com> (raw)
In-Reply-To: <CAOfbx2YKcUOMcOxc==rgLOAum5i=4zqhB132Q3QWoVpw04z7cg@mail.gmail.com>
References: <CAOfbx2YKcUOMcOxc==rgLOAum5i=4zqhB132Q3QWoVpw04z7cg@mail.gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-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.
--
View this message in context: http://postgresql.1045698.n5.nabble.com/Re-recently-and-selectively-slow-but-very-simple-update-quer...
Sent from the PostgreSQL - performance mailing list archive at Nabble.com.
--
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: david.g.johnston@gmail.com
Subject: Re: recently and selectively slow, but very simple, update query....
In-Reply-To: <1399326680993-5802555.post@n5.nabble.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox