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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-196) Pig should use '-reducer NONE' for map-only jobs
Date Tue, 08 Apr 2008 16:55:24 GMT
Pig should use '-reducer NONE' for map-only jobs
------------------------------------------------

                 Key: PIG-196
                 URL: https://issues.apache.org/jira/browse/PIG-196
             Project: Pig
          Issue Type: Bug
            Reporter: Arun C Murthy
            Assignee: Arun C Murthy


Currently, for map-only jobs, Pig writes map-outputs directly to HDFS and then sends zero
data to reducers. The problem with this is two fold:
 * Reduce slots are unnecessarily wasted on the cluster
 * Reduces write empty files to HDFS putting pressure on the Namenode

Both these can we very easily avoided by just calling:
{noformat}
job.setNumReduces(0);
{noformat}
and letting Hadoop Map-Reduce take care of writing map-outputs directly to HDFS.

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