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From "Feng Jiang (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-689) hadoop should provide a common way to wrap instances with different types into one type
Date Wed, 08 Nov 2006 03:16:50 GMT
hadoop should provide a common way to wrap instances with different types into one type
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                 Key: HADOOP-689
                 URL: http://issues.apache.org/jira/browse/HADOOP-689
             Project: Hadoop
          Issue Type: Improvement
          Components: io
         Environment: All environment
            Reporter: Feng Jiang


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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