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From "Feng Jiang (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-839) CLONE -hadoop should provide a common way to wrap instances with different types into one type
Date Wed, 20 Dec 2006 06:21:21 GMT
CLONE -hadoop should provide a common way to wrap instances with different types into one type
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                 Key: HADOOP-839
                 URL: http://issues.apache.org/jira/browse/HADOOP-839
             Project: Hadoop
          Issue Type: Improvement
          Components: io
         Environment: All environment
            Reporter: Feng Jiang
             Fix For: 0.9.0


When two sequence files, which have same Key type but different Value types, are mapped out
to reduce, multiple Value types is not allowed. In this case, we need a way to wrap instances
with different types into one class type to reduce.

In current code, ObjectWritable is a sole choice. but it costs too many space, because the
class declaration will be appended into output file as a string for every Key-value pair.

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