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From "Tim Smith (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1754) Get rid of NonMatchingScorer from BooleanScorer2
Date Tue, 21 Jul 2009 18:04:14 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1754?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12733756#action_12733756
] 

Tim Smith commented on LUCENE-1754:
-----------------------------------

Here's a couple of use cases where a Query should rewrite to null/NonMatchingQuery (in my
opinion):
* Wildcard query that maps to 0 terms in the index
* range query that again maps to 0 terms in the index
* boolean query that has 0 clauses
* filter based constant score query that has 0 docs in it
* (and thats just in the in the lucene tree, nothing to do with custom query implementations)

Most of these situations would actually preempt needing to return null from a scorer, since
the query would already have been rewritten to a NonMatchingQuery/null prior to asking for
a scorer

BooleanQuery could then also do instanceof checks on return from clause rewrite. If a NonMatchingQuery/null
is returned for a required clause, the BooleanQuery itself can rewrite to NonMatchingQuery,
also, if a prohibited clause rewrites to NonMatchingQuery/null, that clause can be removed
entirely, if an optional clause rewrites to NonMatchingQUery/null, that clause can also be
removed safely

> Get rid of NonMatchingScorer from BooleanScorer2
> ------------------------------------------------
>
>                 Key: LUCENE-1754
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1754
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>            Reporter: Shai Erera
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 2.9
>
>         Attachments: LUCENE-1754.patch
>
>
> Over in LUCENE-1614 Mike has made a comment about removing NonMatchinScorer from BS2,
and return null in BooleanWeight.scorer(). I've checked and this can be easily done, so I'm
going to post a patch shortly. For reference: https://issues.apache.org/jira/browse/LUCENE-1614?focusedCommentId=12715064&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12715064.
> I've marked the issue as 2.9 just because it's small, and kind of related to all the
search enhancements done for 2.9.

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