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https://issues.apache.org/jira/browse/LUCENE-2880?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12985387#action_12985387
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Paul Elschot commented on LUCENE-2880:
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A related problem is that Spans does not have a weight (or whatever factor) of
its own.
Currently Spans can only be scored at the top level (by SpanScorer) and not
when they are nested.
In the nested case the only way to affect to score value is via the length.
> SpanQuery scoring inconsistencies
> ---------------------------------
>
> Key: LUCENE-2880
> URL: https://issues.apache.org/jira/browse/LUCENE-2880
> Project: Lucene - Java
> Issue Type: Bug
> Reporter: Robert Muir
> Fix For: 4.0
>
> Attachments: LUCENE-2880.patch
>
>
> Spinoff of LUCENE-2879.
> You can see a full description there, but the gist is that SpanQuery sums up
> freqs with "sloppyFreq".
> However this slop is simply spans.end() - spans.start()
> For a SpanTermQuery for example, this means its scoring 0.5 for TF versus
> TermQuery's 1.0.
> As you can imagine, I think in practical situations this would make it
> difficult for SpanQuery users to
> really use SpanQueries for effective ranking, especially in combination with
> non-Spanqueries (maybe via DisjunctionMaxQuery, etc)
> The problem is more general than this simple example: for example
> SpanNearQuery should be consistent with PhraseQuery's slop.
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