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https://issues.apache.org/jira/browse/LUCENE-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12704522#action_12704522
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Shai Erera commented on LUCENE-1614:
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I think I understand what you mean, but please correct me if I'm wrong. You
propose this check() so that in case a DISI can save any extra operations it
does in next() (such as reading a payload for example) it will do so. Therefore
in the example you give above with CS, next()'s contract forces it to advance
all the sub-scorers, but with check() it could stop in the middle.
This warrants an explicit documentation and implementation by current DISIs ...
I don't think that if you call a DISI today with next(10) and next(10) it will
not move to 11 in the second call. But calling check(10) and next(10) MUST not
advance the DISI further than 10. If the default impl in DISI just uses
nextDoc() and returns true if the return value is the requested, we should be
safe back-compat-wise, but this is still dangerous and we need clear
documentation.
BTW, perhaps a testAndSet-like version can save check(10) followed by a
next(10), and will fit nicer?
> 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
>
>
> 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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