[jira] [Commented] (LUCENE-6198) two phase intersection

["David Smiley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-6198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14378276#comment-14378276 ] 

David Smiley commented on LUCENE-6198:
--------------------------------------

Having seen the TwoPhaseIterator in use and coded to its API, I think there is room for streamlining it a bit.  Almost all implementations have an approximation() method that returns a DISI that was already constructed, and the couple that don't are simple constructors to a DISI anyway.  Well then TwoPhaseIterator could take it in its constructor, put it on a field, and then return it from approximation() as a default implementation.

TwoPhaseIterator's javadocs should make a reference to Scorer.asTwoPhaseIterator.

Why is Scorer.asTwoPhaseIterator on Scorer and not DocIdSetIterator?  It would make this capability more general.

> two phase intersection
> ----------------------
>
>                 Key: LUCENE-6198
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6198
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Robert Muir
>            Assignee: David Smiley
>             Fix For: Trunk, 5.1
>
>         Attachments: LUCENE-6198.patch, LUCENE-6198.patch, LUCENE-6198.patch, LUCENE-6198.patch, LUCENE-6198.patch, phrase_intersections.tasks
>
>
> Currently some scorers have to do a lot of per-document work to determine if a document is a match. The simplest example is a phrase scorer, but there are others (spans, sloppy phrase, geospatial, etc).
> Imagine a conjunction with two MUST clauses, one that is a term that matches all odd documents, another that is a phrase matching all even documents. Today this conjunction will be very expensive, because the zig-zag intersection is reading a ton of useless positions.
> The same problem happens with filteredQuery and anything else that acts like a conjunction.



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