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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] Reopened: (LUCENE-1453) When reopen returns a new IndexReader, both IndexReaders may now control the lifecycle of the underlying Directory which is managed by reference counting
Date Sun, 07 Jun 2009 22:28:07 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-1453?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Uwe Schindler reopened LUCENE-1453:
-----------------------------------


After some testing, I found out, that this issue is not fixed. The test "TestIndexReaderReopen"
fails very often, if all occurences of FSDirectory.getDirectory() are replaced by FSDirectory.open()
in IndexReader/IndexWriter and DirectoryReader.
open() returns non refcounting single-use directorys that can be closed only one time. If
readers on top of this (using the now-deprecated File/String IndexReader.open()) are reopened
the directories are sometimes closed false.
I was hoping, LUCENE-1651 fixes this, but this is not so.

There are two possibilities to fix this:
For both, the first step is to remove the whole closeDir stuff from all IndexReaders and do
not close it from within indexReader.
Then there are two solutions:
- As FSDir.open() only returns subclasses of FSDir that have a no-op close() method, no closing
is required. So we can just leave them open
- Another possibility is to wrap all readers opened by IR.open() with File/String param by
an (deprecated, package private) FilterIndexReader that handles closing the directory in close()
and reopen() in a proper way. This is much simplier than doing it inside the DirectoryReader
reopen stuff. The small overhead in passing through FilterIndexReader only affects people
using the deprecated File/String open() methods. Users, directly using FSDir & Co. have
no slowdown.

> When reopen returns a new IndexReader, both IndexReaders may now control the lifecycle
of the underlying Directory which is managed by reference counting
> ---------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-1453
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1453
>             Project: Lucene - Java
>          Issue Type: Bug
>    Affects Versions: 2.4
>            Reporter: Mark Miller
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 2.4.1, 2.9
>
>         Attachments: LUCENE-1453.patch, LUCENE-1453.patch, LUCENE-1453.patch
>
>
> Rough summary. Basically, FSDirectory tracks references to FSDirectory and when IndexReader.reopen
shares a Directory with a created IndexReader and closeDirectory is true, FSDirectory's ref
management will see two decrements for one increment. You can end up getting an AlreadyClosed
exception on the Directory when the IndexReader is open.
> I have a test I'll put up. A solution seems fairly straightforward (at least in what
needs to be accomplished).

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