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Message-ID: <4BA1403D.9030402@2ndquadrant.com>
Date: Wed, 17 Mar 2010 16:49:01 -0400
From: Greg Smith <greg@2ndquadrant.com>
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To: Alvaro Herrera <alvherre@commandprompt.com>
CC: Andres Freund <andres@anarazel.de>, pgsql-performance@postgresql.org,
	Rob Wultsch <wultsch@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Building multiple indexes concurrently
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Alvaro Herrera wrote:
> Andres Freund escribió:
>
>   
>> I find it way much easier to believe such issues exist on a tables in 
>> constrast to indexes. The likelihood to get sequential accesses on an index is 
>> small enough on a big table to make it unlikely to matter much.
>>     
>
> Vacuum walks indexes sequentially, for one.
>   

That and index-based range scans were the main two use-cases I was 
concerned would be degraded by interleaving index builds, compared with 
doing them in succession.  I work often with time-oriented apps that 
have heavy "give me every record between <a> and <b>" components to 
them, and good sequential index performance can be an important 
requirement for that kind of application.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us