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Re: external sort performance

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: external sort performance
Date: 2011-11-18 00:46:05
Message-ID: 4EC5AACD.9010802@agliodbs.com (view raw or flat)
Thread:
Lists: pgsql-performance
> The first log statement is expected. The second log statement, however, isn't.
> The total table size is (as noted earlier) about 5GB and, in fact, fit
> into one nice hash table (approx 15GB in size).
> Is the sorting that is necessary for index creation unable to use a
> hash table? (This is a standard btree index).

How big is the source table?  You're not sorting the *result* table,
you're sorting the source table if you're summarizing it.

If the original source data is only 5GB, I'd check your code for a
cartesian join.

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

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