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From "Shai Erera (JIRA)" <>
Subject [jira] Commented: (LUCENE-1614) Add next() and skipTo() variants to DocIdSetIterator that return the current doc, instead of boolean
Date Fri, 29 May 2009 10:48:45 GMT


Shai Erera commented on LUCENE-1614:

I don't like that code also. But if we allow to return any value, except -1 or NO_MORE_DOCS
before the iteration started, someone will have very hard time trying to write such code (to
determine if the iterator has started).

The current contract already specifies what this method should return when nextDoc or advance
were not called. We just need to make it more explicit:
* Return -1 if the iteration did not start, and there are documents to return
* Return NO_MORE_DOCS if there are no more docs to return (whether the iteration started or
* Return the doc ID on any other case..

Note that I also wrote that this method should not throw any exception, but I think of relaxing
that either, and say "it is better if the implementation does not throw any exception in case
there are no more documents to return". The reason is, we cannot force "don't throw exception"
in the code ... What do you think?

I will update the patch if you agree to these changes.

> Add next() and skipTo() variants to DocIdSetIterator that return the current doc, instead
of boolean
> ----------------------------------------------------------------------------------------------------
>                 Key: LUCENE-1614
>                 URL:
>             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
> See
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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