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Posted to common-issues@hadoop.apache.org by "Hudson (JIRA)" <ji...@apache.org> on 2011/03/01 08:17:37 UTC
[jira] Commented: (HADOOP-7151) Document need for stable hashCode()
in WritableComparable
[ https://issues.apache.org/jira/browse/HADOOP-7151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13000758#comment-13000758 ]
Hudson commented on HADOOP-7151:
--------------------------------
Integrated in Hadoop-Common-trunk #616 (See [https://hudson.apache.org/hudson/job/Hadoop-Common-trunk/616/])
HADOOP-7151. Document need for stable hashCode() in WritableComparable. Contributed by Dmitriy V. Ryaboy.
> Document need for stable hashCode() in WritableComparable
> ---------------------------------------------------------
>
> Key: HADOOP-7151
> URL: https://issues.apache.org/jira/browse/HADOOP-7151
> Project: Hadoop Common
> Issue Type: Bug
> Reporter: Dmitriy V. Ryaboy
> Assignee: Dmitriy V. Ryaboy
> Priority: Minor
> Fix For: 0.23.0
>
> Attachments: HADOOP-7151.patch, HADOOP-7151.patch
>
>
> When a Writable is used as a key, HashPartitioner implicitly assumes that hashCode() will return the same value across different instances of the JVM. This is not a guaranteed behavior in Java, and Object's default hashCode() does not in fact do this, which can lead to subtle bugs. This requirement should be explicitly called out.
> In addition the sample MyWritable in the javadoc for WritableComparable does not implement hashCode() and thus has a bug. That should be fixed.
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