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