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https://issues.apache.org/jira/browse/LUCENE-6425?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Adrien Grand resolved LUCENE-6425.
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       Resolution: Fixed
    Fix Version/s: 5.2
                   Trunk

> Move extractTerms to Weight
> ---------------------------
>
>                 Key: LUCENE-6425
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6425
>             Project: Lucene - Core
>          Issue Type: Task
>            Reporter: Adrien Grand
>            Assignee: Adrien Grand
>            Priority: Minor
>             Fix For: Trunk, 5.2
>
>         Attachments: LUCENE-6425.patch, LUCENE-6425.patch
>
>
> Today we have extractTerms on Query, but it is supposed to only be called 
> after the query has been specialized to a given IndexReader using 
> Query.rewrite(IndexReader) to allow some complex queries to replace terms 
> "matchers" with actual terms (eg. WildcardQuery).
> However, we already have an abstraction for indexreader-specialized queries: 
> Weight. So I think it would make more sense to have extractTerms on Weight. 
> This would also remove the trap of calling extractTerms on a query which is 
> not rewritten yet.
> Since Weights know about whether scores are needed or not, I also hope this 
> would help improve the extractTerms semantics. We currently have 2 use-cases 
> for extractTerms: distributed IDF and highlighting. While the former only 
> cares about terms which are used for scoring, it could make sense to 
> highlight terms that were used for matching, even if they did not contribute 
> to the score (eg. if wrapped in a ConstantScoreQuery or a BooleanQuery FILTER 
> clause). So highlighters could do searcher.createNormalizedWeight(query, 
> false).extractTerms(termSet) to get all terms that were used for matching the 
> query while distributed IDF would instead do 
> searcher.createNormalizedWeight(query, true).extractTerms(termSet) to get 
> scoring terms only.



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