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From: Greg Smith <greg@2ndQuadrant.com>
To: pgsql-performance@postgresql.org
Subject: Re: bitmask index
Date: Wed, 22 Jun 2011 17:42:25 -0400
Message-ID: <4E0261C1.8000807@2ndQuadrant.com> (raw)
In-Reply-To: <4E025E54.6020402@engene.se>
References: <4E025E54.6020402@engene.se>

On 06/22/2011 05:27 PM, Marcus Engene wrote:
> I have some tables with bitmask integers. Set bits are the interesting 
> ones. Usually they are sparse.

If it's sparse, create a partial index that just includes rows where the 
bit is set:  
http://www.postgresql.org/docs/current/static/indexes-partial.html

You need to be careful the query uses the exact syntax as the one that 
created the index for it to be used.  But if you do that, it should be 
able to pull the rows that match out quickly.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books




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