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Posted to mapreduce-issues@hadoop.apache.org by "Kousuke Saruta (JIRA)" <ji...@apache.org> on 2013/06/28 20:26:21 UTC

[jira] [Commented] (MAPREDUCE-5153) Support for running combiners without reducers

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13695641#comment-13695641 ] 

Kousuke Saruta commented on MAPREDUCE-5153:
-------------------------------------------

Radim, what kind of workload do you want to use combiners without reducers?
We consider whether the feature is really needed or not .
                
> 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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