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From "Uwe Schindler (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3631) Remove write access from SegmentReader and possibly move to separate class or IndexWriter/BufferedDeletes/...
Date Mon, 19 Dec 2011 13:57:30 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13172284#comment-13172284
] 

Uwe Schindler commented on LUCENE-3631:
---------------------------------------

Patch looks nice.

One more thing: In my opinion, the whole synchronized stuff in SegmentCoreReaders can be removed
(see LUCENE-3653) - all is final now, why synchronize? So LUCENE-3653 is a non-issue, when
this is committed. Same applies to IR/DR/... - almost all synchronized methods can go away.

And in my opinion incRef/decRef on IndexReaders is useless, too (or almost useless, except
segmentreaders). As Shai said before, code like SearcherManager should reCount externaly with
a separate interface/helperclass (that refcounts and on decRef to 0, it calls Closeable.close
- so helper can work on any Closeable). But we should remove that in future.
                
> 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.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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