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From "Yonik Seeley (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 Tue, 19 May 2009 19:26:45 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710838#action_12710838
] 

Yonik Seeley commented on LUCENE-1614:
--------------------------------------

> > A bigger question though, is if we should support skipTo(doc) where doc<=current
at all
> I don't think we should support it and it wasn't the intention in the first place. 

OK... I had read your proposal as saying you wanted skipTo(10) twice in a row to return 10
both times (assuming it matched).
Marvin seemed to believe the same thing.

>  In case you disagree, I'd like to ask why is it bad to request the implementation to
remember its state?

I don't disagree, but requiring some implementations to keep and check state would mean less
efficient implementations.

> To me, calling skipTo or advance with the same target multiple times and get different
result every time is weird. I'd like to change that semantic

But I thought we had just agreed that skipTo(doc) is well defined only for doc>current?
(see "bigger question" point above).
If we all agree that , then we don't need to worry about skipTo(10) being called twice in
a row.


> 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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