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From Paul Elschot <>
Subject Re: Span Query Performance
Date Thu, 06 Jan 2005 09:22:57 GMT
On Thursday 06 January 2005 02:17, Andrew Cunningham wrote:
> Hi all,
> I'm currently doing a query similar to the following:
> for w in wordset:
>     query = w near (word1 V word2 V word3 ... V word1422);
>     perform query
> and I am doing this through SpanQuery.getSpans(), iterating through the 
> spans and counting
> the matches, which can result in 4782282 matches (essentially I am only 
> after the match count).
> The query works but the performance can be somewhat slow; so I am wondering:
> a) Would the query potentially run faster if I used 
> with a custom similarity,
> or do both methods essentially use the same mechanics

It would be somewhat slower, because it loops over the getSpans()
and computes document scores and constructs a Hits from the scores.

> b) Does using a RAMDirectory improve query performance any significant 
> amount.

That depends on your operating system, the size of the index, the amount
of RAM you can use, the file buffering efficiency, other loads on the 
computer ...
> c) Is there a faster method to what I am doing I should consider?

Preindexing all word combinations that you're interested in.

Paul Elschot

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