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https://issues.apache.org/jira/browse/HADOOP-9124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534633#comment-13534633
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Karthik Kambatla commented on HADOOP-9124:
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Hi Surenkumar,
Thanks for working on this. The patch looks good - it would be great to have an
associated unit test too.
> 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
> Priority: Minor
> Attachments: 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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