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Date: Tue, 18 Sep 2012 07:27:07 +1100 (NCT)
From: "Robert Muir (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
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Subject: [jira] [Updated] (LUCENE-4403) sharpen javadocs for DISI.docID()
 when unpositioned
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     [ https://issues.apache.org/jira/browse/LUCENE-4403?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Muir updated LUCENE-4403:
--------------------------------

    Attachment: LUCENE-4403.patch

start to a patch. 

As i said the javadocs are ambiguous, an unpositioned DocsEnum can return NO_MORE_DOCS, but you also shouldnt nextDoc() after you see this. 

Because of the ambiguity I'm sure we have test bugs: would be good to have a test postings-format that "caches" (reads ahead or something) to sometimes do this and tickle them out.

                
> sharpen javadocs for DISI.docID() when unpositioned
> ---------------------------------------------------
>
>                 Key: LUCENE-4403
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4403
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>         Attachments: LUCENE-4403.patch
>
>
> Spinoff from LUCENE-4401.
> Currently DISI requires an unpositioned iterator to be -1 or NO_MORE_DOCS. But I think we should refine this: in my opinion NO_MORE_DOCS should mean NO_MORE_DOCS.
> So its ok for it to return NO_MORE_DOCS when its unpositioned, but only if it can already determine that its exhausted.
> This makes life easier on consumers.
> {quote}
> Separately we cant really test this situation very well as long as the javadocs for nextDoc say, Returns the following:
>     -1 or NO_MORE_DOCS if nextDoc() or
>     advance(int) were not called yet.
>     NO_MORE_DOCS if the iterator has exhausted.
>     Otherwise it should return the doc ID it is currently on.
> This prevents us from being able to easily assert that nobody is calling nextDoc()/advance() after the enum is exhausted, since we cannot differentiate 'exhausted' from 'uninitialized'.
> I think we should clarify the javadocs, such that if nextDoc()/advance() are not called yet, you can still return NO_MORE_DOCS, but only if you somehow know you are exhausted-before-you-start. NO_MORE_DOCS should mean NO_MORE_DOCS.
> It could also be everyone reads it this way already, and I'm just being super-anal.
> {quote}
> {quote}
> +1 to sharpen when a DocsEnum can return NO_MORE_DOCS before nextDoc: it should only be if the enum knows it has zero docs. But I'm not even sure we should allow that ... why not always make it -1 ...? We can do that separately...
> {quote}

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