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From "sebastian L. (Commented) (JIRA)" <>
Subject [jira] [Commented] (LUCENE-3440) FastVectorHighlighter: IDF-weighted terms for ordered fragments
Date Sat, 01 Oct 2011 13:17:33 GMT


sebastian L. commented on LUCENE-3440:

Hm, since FieldFragList is created in SimpleFraglistBuilder.createFieldFragList() it should
look more like that: 

 <fragListBuilder name="simple-boosted" class="org.apache.solr.highlight.SimpleFragListBuilder">
  <fragList name="boosted" class=""/>
 <fragListBuilder name="simple-weighted" class="org.apache.solr.highlight.SimpleFragListBuilder"
  <fragList name="weighted" class="">
 <fragmentsBuilder name="ordered" class="org.apache.solr.highlight.ScoreOrderFragmentsBuilder"

> 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-3.5-SNAPSHOT-3440-6.patch,
LUCENE-4.0-SNAPSHOT-3440-6.patch, WeightOrderFragmentsBuilder_table01.html, WeightOrderFragmentsBuilder_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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