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From Kevin Burton <>
Subject Re: Fastest way to fetch N documents with unique keys within large numbers of indexes..
Date Tue, 07 Jun 2005 23:18:48 GMT
Paul Elschot wrote:

>For a large number of indexes, it may be necessary to do this over
>multiple indexes by first getting the doc numbers for all indexes,
>then sorting these per index, then retrieving them
>from all indexes, and repeating the whole thing using terms determined
>from the retrieved docs.
Well this was a BIG win.  Just benchmarking it out shows a 10x -> 50x 
performance increase.

Times in milliseconds:


duration: 1127
duration: 449
duration: 394
duration: 564


duration: 182
duration: 39
duration: 12
duration: 11

The values of 2-4  I'm sure are due to the filesystem buffer cache but I 
can't imagine why they'd be faster in the second round.  It might be 
that Linux is deciding not to buffer the document blocks.



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