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Re: [PERFORM] A Better External Sort?

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Ron Peacetree <rjpeace(at)earthlink(dot)net>
Cc: Dann Corbit <DCorbit(at)connx(dot)com>, pgsql-hackers(at)postgresql(dot)org,pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] A Better External Sort?
Date: 2005-09-27 16:15:06
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackerspgsql-performance

I've somehow missed part of this thread, which is a shame since this is 
an area of primary concern for me.

Your suggested algorithm seems to be designed to relieve I/O load by 
making more use of the CPU.   (if I followed it correctly).  However, 
that's not PostgreSQL's problem; currently for us external sort is a 
*CPU-bound* operation, half of which is value comparisons.  (oprofiles 
available if anyone cares)

So we need to look, instead, at algorithms which make better use of 
work_mem to lower CPU activity, possibly even at the expense of I/O.

--Josh Berkus

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