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Date: Thu, 24 Feb 2011 09:33:38 +0000 (UTC)
From: "Hadoop QA (JIRA)" <jira@apache.org>
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Subject: [jira] Commented: (HADOOP-7153) MapWritable violates contract of
 Map interface for equals() and hashCode()
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    [ https://issues.apache.org/jira/browse/HADOOP-7153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12998782#comment-12998782 ] 

Hadoop QA commented on HADOOP-7153:
-----------------------------------

+1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12471822/7153-mapwritable-equality.combined.diff
  against trunk revision 1074005.

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 3 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 1.3.9) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit warnings.

    +1 core tests.  The patch passed core unit tests.

    +1 contrib tests.  The patch passed contrib unit tests.

    +1 system test framework.  The patch passed system test framework compile.

Test results: https://hudson.apache.org/hudson/job/PreCommit-HADOOP-Build/297//testReport/
Findbugs warnings: https://hudson.apache.org/hudson/job/PreCommit-HADOOP-Build/297//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://hudson.apache.org/hudson/job/PreCommit-HADOOP-Build/297//console

This message is automatically generated.

> MapWritable violates contract of Map interface for equals() and hashCode()
> --------------------------------------------------------------------------
>
>                 Key: HADOOP-7153
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7153
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: io
>    Affects Versions: 0.21.0
>            Reporter: Nicholas Telford
>            Priority: Minor
>         Attachments: 7153-mapwritable-equality-test.diff, 7153-mapwritable-equality.combined.diff, 7153-mapwritable-equality.diff
>
>
> o.a.h.io.MapWritable implements the java.util.Map interface, however it does not define an implementation of the equals() or hashCode() methods; instead the default implementations in java.lang.Object are used.
> This violates the contract of the Map interface which defines different behaviour for equals() and hashCode() than Object does. More information here: http://download.oracle.com/javase/6/docs/api/java/util/Map.html#equals(java.lang.Object)
> The practical consequence is that MapWritables containing equal entries cannot be compared properly. We were bitten by this when trying to write an MRUnit test for a Mapper that outputs MapWritables; the MRUnit driver cannot test the equality of the expected and actual MapWritable objects.

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