[jira] [Commented] (LUCENE-6332) join query scanning "toField" docValue

["Martijn van Groningen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-6332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14352350#comment-14352350 ] 

Martijn van Groningen commented on LUCENE-6332:
-----------------------------------------------

+1 I think it makes sense for the query time join to leverage the `TwoPhaseIterator` optimization. For the scoring based query that is trivial (just override `asTwoPhaseIterator()` method in the scorer), but for the `TermsQuery` is tricker as it seems that via the `MultiTermQuery` the TwoPhaseIterator optimization isn't accessible.

> join query scanning "toField" docValue   
> -----------------------------------------
>
>                 Key: LUCENE-6332
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6332
>             Project: Lucene - Core
>          Issue Type: New Feature
>          Components: modules/join
>    Affects Versions: 5.0
>            Reporter: Mikhail Khludnev
>
> I want to contribute the subj which should do something like ..{{WHERE EXISTS (SELECT 1 FROM fromSearcher.search(fromQuery) WHERE fromField=toField)}}. It turns out, that it can be returned by the current method {{createJoinQuery(...ScoreMode.None)}}
> * at first, it should run {{fromQuery}} first, collect {{fromField}} into {{BytesRefHash}} by {{TermsCollector}}, like it's done now
> * then it should return query with _TwoPhase_ Scorer
> * which obtains {{toField}} docValue on {{matches()}} and check term for existence in  {{BytesRefHash}}
> Do you think it's ever useful? if you do, I can bake a patch. 
> Anyway, suggest the better API eg separate method, or enum and actual  name!   



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