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From "Richard Marr (JIRA)" <>
Subject [jira] [Commented] (LUCENE-1690) Morelikethis queries are very slow compared to other search types
Date Mon, 22 Apr 2013 15:03:16 GMT


Richard Marr commented on LUCENE-1690:

[~erickerickson] as far as I know this is still an issue. I'm not aware of any change, although
I haven't re-run the benchmark recently. If I get around to re-running the benchmark I'll
post the results
> Morelikethis queries are very slow compared to other search types
> -----------------------------------------------------------------
>                 Key: LUCENE-1690
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/other
>    Affects Versions: 2.4.1
>            Reporter: Richard Marr
>            Priority: Minor
>         Attachments: LruCache.patch, LUCENE-1690.patch, 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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