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https://issues.apache.org/jira/browse/LUCENE-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12715104#action_12715104
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Shai Erera commented on LUCENE-1614:
------------------------------------

bq. So I think the solution is to make sure Scorers which do not have a 
nextDoc() should not be passed to CS in the first place. And remove this check 
from CS ctor.

I'm afraid that's impossible too, since CS advances all Scorers in its ctor to 
the first agreed-upon doc ID, which may result in NO_MORE_DOCS right upfront.

What if we document that you shouldn't call nextDoc() after it return 
NO_MORE_DOCS for now, and then maybe we do proceed (in another issue) with the 
DISI.start() method. Then CS can implement start() and return false if there 
are no more docs?

I also tried changing BS2.score(Collector) to first check the docID of 
countingSumScorer, but that is not good either, since a Scorer is allowed to 
return -1 or NO_MORE_DOCS before nextDoc() was called ...

What do you think?

> Add next() and skipTo() variants to DocIdSetIterator that return the current 
> doc, instead of boolean
> ----------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-1614
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1614
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>            Reporter: Shai Erera
>             Fix For: 2.9
>
>         Attachments: LUCENE-1614.patch, LUCENE-1614.patch, LUCENE-1614.patch, 
> LUCENE-1614.patch, LUCENE-1614.patch, LUCENE-1614.patch, LUCENE-1614.patch, 
> LUCENE-1614.patch, LUCENE-1614.patch, LUCENE-1614.patch
>
>
> See 
> http://www.nabble.com/Another-possible-optimization---now-in-DocIdSetIterator-p23223319.html
>  for the full discussion. The basic idea is to add variants to those two 
> methods that return the current doc they are at, to save successive calls to 
> doc(). If there are no more docs, return -1. A summary of what was discussed 
> so far:
> # Deprecate those two methods.
> # Add nextDoc() and skipToDoc(int) that return doc, with default impl in DISI 
> (calls next() and skipTo() respectively, and will be changed to abstract in 
> 3.0).
> #* I actually would like to propose an alternative to the names: advance() 
> and advance(int) - the first advances by one, the second advances to target.
> # Wherever these are used, do something like '(doc = advance()) >= 0' instead 
> of comparing to -1 for improved performance.
> I will post a patch shortly

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