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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9124) SortedMapWritable violates contract of Map interface for equals() and hashCode()
Date Tue, 18 Dec 2012 04:34:14 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13534633#comment-13534633

Karthik Kambatla commented on HADOOP-9124:

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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