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Date: Tue, 30 Nov 2010 15:00:18 -0500 (EST)
From: "Uwe Schindler (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-2779) Use ConcurrentHashMap in
 RAMDirectory
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    [ https://issues.apache.org/jira/browse/LUCENE-2779?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965396#action_12965396 ] 

Uwe Schindler commented on LUCENE-2779:
---------------------------------------

Code looks good, I would only chnage the comment to simply say, that:
{code}
return fileMap.keySet().toArray(new String[0]);
{code}
only works correct in Suns JVM. The thing with new ArrayList(Collection) or any other thing is implemented different in every JVM (even new HashSet(Collection) can be broken if it uses toArray() for some weird reason). But just to note, according to the JDK documentation the above code should work - period. So we should only document that and say, that this is broken.


> Use ConcurrentHashMap in RAMDirectory
> -------------------------------------
>
>                 Key: LUCENE-2779
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2779
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Store
>            Reporter: Shai Erera
>            Assignee: Shai Erera
>            Priority: Minor
>             Fix For: 3.1, 4.0
>
>         Attachments: LUCENE-2779-backwardsfix.patch, LUCENE-2779.patch, LUCENE-2779.patch, LUCENE-2779.patch, TestCHM.java
>
>
> RAMDirectory synchronizes on its instance in many places to protect access to map of RAMFiles, in addition to updating the sizeInBytes member. In many places the sync is done for 'read' purposes, while only in few places we need 'write' access. This looks like a perfect use case for ConcurrentHashMap
> Also, syncing around sizeInBytes is unnecessary IMO, since it's an AtomicLong ...
> I'll post a patch shortly.

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