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https://issues.apache.org/jira/browse/LUCENE-3631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13229687#comment-13229687
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Aliaksandr Zhuhrou commented on LUCENE-3631:
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Yes. I thought on something like that. I see that lucene enforces a write-once
policy (as I understand this needed to support a transactional behaviour). So I
think we may use some conbination of approach for the LUCENE-3837 and a
current segment system where any updates after commit go to the a new file like
we do with segments. And when the docValues will be read to a memory we will
fetch all files and values in a file with higher generation will override
values with same docIds.
Of course it increases even more the total amount of files. And not sure yet
how to express this updates on level of the IndexWriter api.
> Remove write access from SegmentReader and possibly move to separate class or
> IndexWriter/BufferedDeletes/...
> -------------------------------------------------------------------------------------------------------------
>
> Key: LUCENE-3631
> URL: https://issues.apache.org/jira/browse/LUCENE-3631
> Project: Lucene - Java
> Issue Type: Task
> Components: core/index
> Affects Versions: 4.0
> Reporter: Uwe Schindler
> Assignee: Michael McCandless
> Attachments: LUCENE-3631-threadlocals.patch, LUCENE-3631.patch,
> LUCENE-3631.patch
>
>
> After LUCENE-3606 is finished, there are some TODOs:
> SegmentReader still contains (package-private) all delete logic including
> crazy copyOnWrite for validDocs Bits. It would be good, if SegmentReader
> itsself could be read-only like all other IndexReaders.
> There are two possibilities to do this:
> # the simple one: Subclass SegmentReader and make a RWSegmentReader that is
> only used by IndexWriter/BufferedDeletes/... DirectoryReader will only use
> the read-only SegmentReader. This would move all TODOs to a separate class.
> It's reopen/clone method would always create a RO-SegmentReader (for NRT).
> # Remove all write and commit stuff from SegmentReader completely and move it
> to IndexWriter's readerPool (it must be in readerPool as deletions need a
> not-changing view on an index snapshot).
> Unfortunately the code is so complicated and I have no real experience in
> those internals of IndexWriter so I did not want to do it with LUCENE-3606, I
> just separated the code in SegmentReader and marked with TODO. Maybe Mike
> McCandless can help :-)
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