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Message-ID: <4C1BD4A1.4070406@gmail.com>
Date: Fri, 18 Jun 2010 22:18:41 +0200
From: Yeb Havinga <yebhavinga@gmail.com>
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To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
CC: Greg Smith <greg@2ndquadrant.com>, Matthew Wakeling <matthew@flymine.org>,
	Eliot Gable <egable+pgsql-performance@gmail.com>,
	Robert Haas <robertmhaas@gmail.com>, pgsql-performance@postgresql.org
Subject: Re: B-Heaps
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	<4C1BB294.8070806@2ndquadrant.com> <4C1BBB39.10308@gmail.com>
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Kevin Grittner wrote:
> Yeb Havinga <yebhavinga@gmail.com> wrote:
>  
>   
>> concerning gist indexes:
>>
>> 1) with larger block sizes and hence, larger # entries per gist
>> page, results in more generic keys of those pages. This in turn
>> results in a greater number of hits, when the index is queried, so
>> a larger part of the index is scanned. NB this has nothing to do
>> with caching / cache sizes; it holds for every IO model. Tests
>> performed by me showed performance improvements of over 200%.
>> Since then implementing a speedup has been on my 'want to do
>> list'.
>>     
>  
> As I recall, the better performance in your tests was with *smaller*
> GiST pages, right?  (The above didn't seem entirely clear on that.)
>   
Yes, making pages smaller made index scanning faster.

-- Yeb