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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-4251) The reducer output is not created if the mapper input is empty
Date Tue, 23 Sep 2008 20:39:44 GMT
The reducer output is not created if the mapper input is empty
--------------------------------------------------------------

                 Key: HADOOP-4251
                 URL: https://issues.apache.org/jira/browse/HADOOP-4251
             Project: Hadoop Core
          Issue Type: Bug
          Components: mapred
            Reporter: Namit Jain
            Assignee: Namit Jain


For some Hive stuff, I ran into the following scenario:

For a given map-reduce job, the input was empty. Because of that no mappers and reducers were
created. It would have been helpful if an empty output for the reducer would have been created.

After browsing though the code, it seems that in initTasks() in JobInProgress, no mappers
and reducers are initialized if input is empty.

I was thinking of putting a fix there. If the input is empty, before returning, create the
output directory (as specified by the reducer) if needed.Any comments/suggestions....

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