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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-6881) The efficient comparators aren't always used except for BytesWritable and Text
Date Mon, 26 Jul 2010 22:14:17 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-6881?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Doug Cutting updated HADOOP-6881:
---------------------------------

    Status: Open  (was: Patch Available)

> 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, 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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