From: Franck Routier <franck.routier@axege.com>
To: Nikolas Everett <nik9000@gmail.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: What happens between end of explain analyze and end of query execution ?
Date: Thu, 04 Apr 2013 17:44:05 +0200
Message-ID: <515D9FC5.7030105@axege.com> (raw)
In-Reply-To: <CAPmjWd100eemBz1RTw=r24zgh8+YO8iq86fThqsALznrPuyWqg@mail.gmail.com>
References: <515D92BF.5000309@axege.com>
<CAPmjWd100eemBz1RTw=r24zgh8+YO8iq86fThqsALznrPuyWqg@mail.gmail.com>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-performance>
Right, explain alone takes 3.6 seconds, so the time really seems to go
query planning...
Le 04/04/2013 17:01, Nikolas Everett a écrit :
> We had a problem where the actual query planning time blew up and took
> way more time then the query execution. We reproduced the problem by
> forming a new connection and then just explaining the query. If that
> takes more than a couple of milliseconds you likely have the problem.
> The second plan was fast.
>
> We then dtraced the backend process for a new connection and found
> that opening files had become super slow. In our case this was caused
> by running the database on nfs.
>
> Good luck,
>
> Nik
>
>
> On Thu, Apr 4, 2013 at 10:48 AM, Franck Routier
> <franck.routier@axege.com <mailto:franck.routier@axege.com>> wrote:
>
> Hi,
>
> I have query that should be quick, and used to be quick, but is
> not anymore... Explain analyze can be seen here
> http://explain.depesz.com/s/cpV
> but it is fundamentaly quick : Total runtime: 0.545 ms.
>
> But query execution takes 3.6 seconds. Only 12 rows are returned.
> Adding a limit 1 has no influence.
>
> Postgresql client and server are on the same server, on localhost.
>
> I wonder where my 3.5 seconds are going....
>
> Notice that there is no fancy configuration to tell Postgresql to
> evaluate every query plan on earth, that is gecoxxxx settings are
> on their default values.
>
> Any idea on what can be happening that takes so long ?
>
> Franck
>
>
Attachments:
smime.p7s (application/pkcs7-signature, 4.4K) download
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: franck.routier@axege.com, nik9000@gmail.com
Subject: Re: What happens between end of explain analyze and end of query execution ?
In-Reply-To: <515D9FC5.7030105@axege.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