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From "Richard Marr (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-1690) Morelikethis queries are very slow compared to other search types
Date Sat, 13 Jun 2009 06:15:07 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-1690?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Richard Marr updated LUCENE-1690:
---------------------------------

    Attachment: LUCENE-1690.patch

This patch implements a basic hashmap term frequency cache. It shouldn't affect any applications
that don't opt-in to using it, and applications that do should see an order of magnitude performance
improvement for MLT queries.

This cache implementation is tied to the MLT object but can be cleared on demand.

> Morelikethis queries are very slow compared to other search types
> -----------------------------------------------------------------
>
>                 Key: LUCENE-1690
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1690
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: contrib/*
>    Affects Versions: 2.4.1
>            Reporter: Richard Marr
>            Priority: Minor
>         Attachments: LUCENE-1690.patch
>
>   Original Estimate: 2h
>  Remaining Estimate: 2h
>
> The MoreLikeThis object performs term frequency lookups for every query.  From my testing
that's what seems to take up the majority of time for MoreLikeThis searches.  
> For some (I'd venture many) applications it's not necessary for term statistics to be
looked up every time. A fairly naive opt-in caching mechanism tied to the life of the MoreLikeThis
object would allow applications to cache term statistics for the duration that suits them.
> I've got this working in my test code. I'll put together a patch file when I get a minute.
From my testing this can improve performance by a factor of around 10.

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