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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-6881) The efficient comparators aren't always used except for BytesWritable and Text
Date Mon, 26 Jul 2010 18:53:16 GMT
The efficient comparators aren't always used except for BytesWritable and Text
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                 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


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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