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Date: Mon, 6 Feb 2012 13:13:59 +0000 (UTC)
From: "Jon Steinich (Commented) (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
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Subject: [jira] [Commented] (DERBY-5603) EmbedConnection.clearLOBMapping()
 incorrectly clears lobFiles causing a ConcurrentModificationException
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    [ https://issues.apache.org/jira/browse/DERBY-5603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13201263#comment-13201263 ] 

Jon Steinich commented on DERBY-5603:
-------------------------------------

I haven't verified a simple reproduce case, but pre-patch it should have failed whenever there was more than one entry in the lobFIles Set, so I believe creating 2 blobs in a single transaction would cause it.
                
> EmbedConnection.clearLOBMapping() incorrectly clears lobFiles causing a ConcurrentModificationException
> -------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-5603
>                 URL: https://issues.apache.org/jira/browse/DERBY-5603
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions: 10.5.1.1, 10.8.2.2
>         Environment: Win 7 64 bit
> JDK 1.6.0_24
>            Reporter: Jon Steinich
>            Assignee: Kristian Waagan
>            Priority: Critical
>         Attachments: derby-5603-1a-avoid_concurrentmodification.diff
>
>   Original Estimate: 1h
>  Remaining Estimate: 1h
>
> In EmbedConnection.clearLOBMapping()  the code which iterates over lobFiles has a finally block which clears the Set.  This causes a ConcurrentModificationException to be thrown and even using a concurrent data structure would still result in only one LOBFile being correctly closed.
> This will occur anytime the lobFiles Set contains more than 1 LOBFile.
> Stack Trace:
> java.sql.SQLException: Java exception: ': java.util.ConcurrentModificationException'. 
>  at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source) 
>  at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source) 
>  at org.apache.derby.impl.jdbc.Util.javaException(Unknown Source) 
>  at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown Source) 
>  at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown Source) 
>  at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown Source) 
>  at org.apache.derby.impl.jdbc.EmbedConnection.commit(Unknown Source) 
> <lines removed>
> Caused by: java.sql.SQLException: Java exception: ': java.util.ConcurrentModificationException'. 
>  at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source) 
>  at org.apache.derby.impl.jdbc.SQLExceptionFactory40.wrapArgsForTransportAcrossDRDA(Unknown Source) 
>  ... 16 more 
> Caused by: java.util.ConcurrentModificationException 
>  at java.util.HashMap$HashIterator.nextEntry(Unknown Source) 
>  at java.util.HashMap$KeyIterator.next(Unknown Source) 
>  at org.apache.derby.impl.jdbc.EmbedConnection.clearLOBMapping(Unknown Source) 
>  ... 10 more

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