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From "sebastian L. (Updated) (JIRA)" <>
Subject [jira] [Updated] (LUCENE-3440) FastVectorHighlighter: IDF-weighted terms for ordered fragments
Date Wed, 23 Nov 2011 15:41:40 GMT


sebastian L. updated LUCENE-3440:

    Attachment:     (was: LUCENE-4.0-SNAPSHOT-3440-9.patch)
> FastVectorHighlighter: IDF-weighted terms for ordered fragments 
> ----------------------------------------------------------------
>                 Key: LUCENE-3440
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: modules/highlighter
>    Affects Versions: 3.5, 4.0
>            Reporter: sebastian L.
>            Priority: Minor
>              Labels: FastVectorHighlighter
>             Fix For: 3.5, 4.0
>         Attachments: LUCENE-3440.patch, LUCENE-3440.patch, LUCENE-4.0-SNAPSHOT-3440-9.patch,
weight-vs-boost_table01.html, weight-vs-boost_table02.html
> The FastVectorHighlighter uses for every term found in a fragment an equal weight, which
causes a higher ranking for fragments with a high number of words or, in the worst case, a
high number of very common words than fragments that contains *all* of the terms used in the
original query. 
> This patch provides ordered fragments with IDF-weighted terms: 
> total weight = total weight + IDF for unique term per fragment * boost of query; 
> The ranking-formula should be the same, or at least similar, to that one used in
> The patch is simple, but it works for us. 
> Some ideas:
> - A better approach would be moving the whole fragments-scoring into a separate class.
> - Switch scoring via parameter 
> - Exact phrases should be given a even better score, regardless if a phrase-query was
executed or not
> - edismax/dismax-parameters pf, ps and pf^boost should be observed and corresponding
fragments should be ranked higher 

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