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Date: Fri, 1 Feb 2013 17:14:13 +0000 (UTC)
From: "Karthik Kambatla (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Message-ID: <JIRA.12622997.1354928159282.230131.1359738853939@arcas>
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Subject: [jira] [Updated] (HADOOP-9124) SortedMapWritable violates contract
 of Map interface for equals() and hashCode()
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     [ https://issues.apache.org/jira/browse/HADOOP-9124?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Karthik Kambatla updated HADOOP-9124:
-------------------------------------

    Attachment: hadoop-9124-branch1.patch

Thanks Tom for committing this.

Suren - sorry for the delay. branch-1 is the dev branch for 1.x.y releases. Similarly, branch-2 is for 2.x.y. The directory structure for trunk, branch-2 and branch-0.23 is the same, but branch-1 is different. Hence, the need for a separate branch-1 patch.

I have copied the changes from here verbatim to branch-1, verified the test passes. Suren - are you OK with this?

Tom - can you commit this to branch-1?
                
> SortedMapWritable violates contract of Map interface for equals() and hashCode()
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-9124
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9124
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: io
>    Affects Versions: 2.0.2-alpha
>            Reporter: Patrick Hunt
>            Assignee: Surenkumar Nihalani
>            Priority: Minor
>             Fix For: 2.0.3-alpha
>
>         Attachments: hadoop-9124-branch1.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch, HADOOP-9124.patch
>
>
> This issue is similar to HADOOP-7153. It was found when using MRUnit - see MRUNIT-158, specifically https://issues.apache.org/jira/browse/MRUNIT-158?focusedCommentId=13501985&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13501985
> --
> o.a.h.io.SortedMapWritable 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 SortedMapWritables 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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