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From "Radim Kolar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5153) Support for running combiners without reducers
Date Fri, 28 Jun 2013 23:03:21 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13695900#comment-13695900
] 

Radim Kolar commented on MAPREDUCE-5153:
----------------------------------------

Result aggregation. It does not needs to be perfect, because its going to be stored in HIVE.
                
> Support for running combiners without reducers
> ----------------------------------------------
>
>                 Key: MAPREDUCE-5153
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5153
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>            Reporter: Radim Kolar
>
> scenario: Workflow mapper -> sort -> combiner -> hdfs
> No api change is need, if user set combiner class and reducers = 0 then run combiner
and sent output to HDFS.
> Popular libraries such as scalding and cascading are offering this functionality, but
they use caching entire mapper output in memory.

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