Re: Performance question 83 GB Table 150 million rows, distinct select

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Performance question 83 GB Table 150 million rows, distinct select
Date: 2011-11-17 05:19:01
Message-ID: 4EC49945.40408@agliodbs.com
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Tory,

A seq scan across 83GB in 4 minutes is pretty good. That's over
300MB/s. Even if you assume that 1/3 of the table was already cached,
that's still over 240mb/s. Good disk array.

Either you need an index, or you need to not do this query at user
request time. Or a LOT more RAM.

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

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