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From "Mike Sokolov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3234) Provide limit on phrase analysis in FastVectorHighlighter
Date Thu, 23 Jun 2011 18:13:47 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3234?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13054010#comment-13054010
] 

Mike Sokolov commented on LUCENE-3234:
--------------------------------------

Yes, although a smaller number might be fine.  Maybe Koji will comment: I don't completely
understand the scaling here, but it seemed to me that I had a case with around 2000 occurrences
of a term that lead to a 15-20 sec evaluation time on my desktop.  The max value will be an
int, sire, although I think the number is going to scale like positions, not offsets FWIW.


> Provide limit on phrase analysis in FastVectorHighlighter
> ---------------------------------------------------------
>
>                 Key: LUCENE-3234
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3234
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: Mike Sokolov
>         Attachments: LUCENE-3234.patch
>
>
> With larger documents, FVH can spend a lot of time trying to find the best-scoring snippet
as it examines every possible phrase formed from matching terms in the document.  If one is
willing to accept
> less-than-perfect scoring by limiting the number of phrases that are examined, substantial
speedups are possible.  This is analogous to the Highlighter limit on the number of characters
to analyze.
> The patch includes an artifical test case that shows > 1000x speedup.  In a more normal
test environment, with English documents and random queries, I am seeing speedups of around
3-10x when setting phraseLimit=1, which has the effect of selecting the first possible snippet
in the document.  Most of our sites operate in this way (just show the first snippet), so
this would be a big win for us.
> With phraseLimit = -1, you get the existing FVH behavior. At larger values of phraseLimit,
you may not get substantial speedup in the normal case, but you do get the benefit of protection
against blow-up in pathological cases.

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