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Re: Better default_statistics_target

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Greg Sabino Mullane" <greg(at)turnstep(dot)com>, <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Better default_statistics_target
Date: 2007-11-19 08:15:17
Message-ID: 87ejemvega.fsf@oxford.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:

> Long text fields that might use LIKE should be set to 100. CHAR(1) and
> general fields should be set to 10.

I could see arguing that either way. Longer fields are capable of more
precision and so may need more buckets to predict. On the other hand longer
fields take more space and take longer to compare so to make consistent use of
resources you would want to avoid storing and comparing large numbers of them
whereas you could afford much larger targets for small quick columns.

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com
  Ask me about EnterpriseDB's Slony Replication support!

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