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Date: Tue, 20 Sep 2011 19:20:08 +0000 (UTC)
From: "S.L. (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
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Subject: [jira] [Updated] (LUCENE-3440) FastVectorHighlighter: IDF-weighted
 terms for ordered fragments
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     [ https://issues.apache.org/jira/browse/LUCENE-3440?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

S.L. updated LUCENE-3440:
-------------------------

    Attachment: LUCENE-3440-1.patch

Ups, wrong patch ... here's the right one.

> FastVectorHighlighter: IDF-weighted terms for ordered fragments 
> ----------------------------------------------------------------
>
>                 Key: LUCENE-3440
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3440
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: modules/highlighter
>    Affects Versions: 3.5
>            Reporter: S.L.
>            Priority: Minor
>              Labels: patch
>             Fix For: 3.5
>
>         Attachments: LUCENE-3440-1.patch, LUCENE-3440.patch
>
>
> 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-formular should be the same, or at least similar, to that one used in org.apache.lucene.search.highlight.QueryTermScorer.
> 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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