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https://issues.apache.org/jira/browse/LUCENE-4403?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Robert Muir updated LUCENE-4403:
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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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