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From "Shai Erera (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1614) Add next() and skipTo() variants to DocIdSetIterator that return the current doc, instead of boolean
Date Wed, 20 May 2009 19:34:45 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12711303#action_12711303
] 

Shai Erera commented on LUCENE-1614:
------------------------------------

Maybe there's a way out of this. In 2.9 we're already changing the contract of DISI with the
new nextDoc and advance. As opposed to before (boolean), we're now stating what these methods
should return when there are no more documents. So what if we do this:

# In 2.9 we document that these methods should return MAX_VAL when there are no more documents.
# Document doc() that in 3.0 it should return MAX_VAL when there are no more docs. Also put
that in CHANGES.
# I change the patch to return MAX_VAL for all current DISIs/Scorers, but don't take advantage
of that yet in BS and ConjunctionScorer.
# I open another issue for 3.0 which will take advantage of that, and ensure all current DISIs/Scorers'
doc() return MAX_VAL when there are no more docs?

I think that should work. We'll need to delay with that optimization beyond 2.9, but I don't
think there's a nice and clean way around it otherwise. If 3.0 should quickly follow 2.9,
we won't wait for long :).

> 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
>
>
> 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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