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Re: Possible to improve query plan?

From: Jeremy Palmer <JPalmer(at)linz(dot)govt(dot)nz>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org"<pgsql-performance(at)postgresql(dot)org>, "andy(at)squeakycode(dot)net"<andy(at)squeakycode(dot)net>
Subject: Re: Possible to improve query plan?
Date: 2011-01-25 00:24:48
Message-ID: 666FB8D75E95AE42965A0E76A5E5337E06D2D27BC3@prdlsmmsg01.ad.linz.govt.nz (view raw or flat)
Thread:
Lists: pgsql-performance
Thanks heaps for the advice. I will do some benchmarks to see how long it takes to cluster all of the database tables.

Cheers,
Jeremy

-----Original Message-----
From: Kevin Grittner [mailto:Kevin(dot)Grittner(at)wicourts(dot)gov] 
Sent: Tuesday, 25 January 2011 1:02 p.m.
To: Jeremy Palmer; Tom Lane
Cc: Robert Haas; pgsql-performance(at)postgresql(dot)org; andy(at)squeakycode(dot)net
Subject: RE: [PERFORM] Possible to improve query plan?

Jeremy Palmer <JPalmer(at)linz(dot)govt(dot)nz> wrote:
 
> My only question is how often will I need to re-cluster the
> table, because it comes at quite a cost.
 
I probably should have mentioned that the CLUSTER will run faster if
the data is already mostly in the right sequence.  You'll be doing a
nearly sequential pass over the heap, which should minimize seek
time, especially if the OS notices the pattern and starts doing
sequential read-ahead.
 
-Kevin
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