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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4080) SegmentReader.numDeletedDocs() sometimes gives an incorrect numDeletedDocs
Date Thu, 28 Jun 2012 11:15:44 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4080?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13403011#comment-13403011
] 

Robert Muir commented on LUCENE-4080:
-------------------------------------

I don't understand the concurrency here but thats what I read from the issue description:
my concern was just that its not obvious in the first patch if we are actually just opening
an SR with an existing core inside this sync or not, and I dont even know if its a problem
:)
                
> SegmentReader.numDeletedDocs() sometimes gives an incorrect numDeletedDocs
> --------------------------------------------------------------------------
>
>                 Key: LUCENE-4080
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4080
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: core/index
>    Affects Versions: 4.0, 4.1
>            Reporter: Adrien Grand
>            Priority: Trivial
>             Fix For: 4.1
>
>         Attachments: LUCENE-4080.patch, LUCENE-4080.patch
>
>
> At merge time, SegmentReader sometimes gives an incorrect value for numDeletedDocs.
> From LUCENE-2357:
> bq. As far as I know, [SegmenterReader.numDeletedDocs() is] only unreliable in this context
(SegmentReader passed to SegmentMerger for merging); this is because we allow newly marked
deleted docs to happen concurrently up until the moment we need to pass the SR instance to
the merger (search for "// Must sync to ensure BufferedDeletesStream" in IndexWriter.java)
... but it would be nice to fix that, so I think open a new issue (it won't block this one)?
We should be able to make a new SR instance, sharing the same core as the current one but
using the correct delCount...
> bq. It would be cleaner (but I think hairier) to create a new SR for merging that holds
the correct delCount, but let's do that under the separate issue.
> bq.  it would be best if the SegmentReader's numDeletedDocs were always correct, but,
fixing that in IndexWriter is somewhat tricky. Ie, the fix could be hairy but the end result
("SegmentReader.numDeletedDocs can always be trusted") would be cleaner...

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