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Subject: Re: index structure for 114-dimension vector
From: Jeff Davis <pgsql@j-davis.com>
To: Andrew Lazarus <andrew@pillette.com>
Cc: pgsql-performance@postgresql.org
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Date: Fri, 20 Apr 2007 14:41:24 -0700
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On Fri, 2007-04-20 at 12:07 -0700, Andrew Lazarus wrote:
> I have a table with 2.5 million real[] arrays. (They are points in a
> time series.) Given a new array X, I'd like to find, say, the 25
> closest to X in some sense--for simplification, let's just say in the
> usual vector norm. Speed is critical here, and everything I have tried
> has been too slow.
> 
> I imported the cube contrib package, and I tried creating an index on
> a cube of the last 6 elements, which are the most important. Then I

Have you tried just making normal indexes on each of the last 6 elements
and see if postgresql will use a BitmapAnd to combine them? 

Regards,
    Jeff Davis