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https://issues.apache.org/jira/browse/HADOOP-6881?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Doug Cutting updated HADOOP-6881:
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Attachment: HADOOP-6881.patch
Here's a version of the patch that adds a unit test. This test fails for me
without the patch.
> The efficient comparators aren't always used except for BytesWritable and Text
> ------------------------------------------------------------------------------
>
> Key: HADOOP-6881
> URL: https://issues.apache.org/jira/browse/HADOOP-6881
> Project: Hadoop Common
> Issue Type: Bug
> Affects Versions: 0.20.0
> Reporter: Owen O'Malley
> Assignee: Owen O'Malley
> Fix For: 0.20.3
>
> Attachments: h-6881.patch, HADOOP-6881.patch
>
>
> When we moved from Java 4 to Java 5 (and then 6), there was a change in the
> JVM semantics such that references to a class such as IntWritable.class no
> longer forces initialization. Since all of the Writables depend on their
> class static blocks to register their fast comparators, that can happen
> *after* we look up the comparator. In that case, the framework will fall back
> to the generic comparator that deserializes both keys and does the object
> compare, which may cause a huge slow down in the sort.
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