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Message-ID: <500A620D.4030505@ringerc.id.au>
Date: Sat, 21 Jul 2012 16:02:21 +0800
From: Craig Ringer <ringerc@ringerc.id.au>
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To: Ioannis Anagnostopoulos <ioannis@anatec.com>
CC: pgsql-performance@postgresql.org
Subject: Re: A very long running query....
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On 07/21/2012 06:19 AM, Ioannis Anagnostopoulos wrote:

> On this Ubuntu installation the default_statistics_target = 1000 and 
> not 100. Do you think that this might be an issue?

Nope. You should generally avoid setting default_statistics_target too 
high anyway; leave it where it is and use ALTER TABLE ... ALTER COLUMN 
... SET STATISTICS to raise the targets on columns where you're seeing 
bad statistics estimates.

http://www.postgresql.org/docs/9.1/static/sql-altertable.html

Also make sure autovaccum is running frequently so it keeps the stats up 
to date.

--
Craig Ringer



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    <div class="moz-cite-prefix">On 07/21/2012 06:19 AM, Ioannis
      Anagnostopoulos wrote:<br>
    </div>
    <br>
    <blockquote cite="mid:5009D963.9040005@anatec.com" type="cite">On
      this Ubuntu installation the default_statistics_target = 1000 and
      not 100. Do you think that this might be an issue?
      <br>
    </blockquote>
    <br>
    Nope. You should generally avoid setting default_statistics_target
    too high anyway; leave it where it is and use ALTER TABLE ... ALTER
    COLUMN ... SET STATISTICS to raise the targets on columns where
    you're seeing bad statistics estimates.<br>
    <br>
    <meta http-equiv="content-type" content="text/html;
      charset=ISO-8859-1">
    <a
      href="http://www.postgresql.org/docs/9.1/static/sql-altertable.html">http://www.postgresql.org/docs/9.1/static/sql-altertable.html</a><br>
    <br>
    Also make sure autovaccum is running frequently so it keeps the
    stats up to date.<br>
    <br>
    --<br>
    Craig Ringer<br>
    <br>
    <br>
  </body>
</html>

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