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Date: Wed, 25 Apr 2007 18:37:15 -0700 (PDT)
From: "Runping Qi (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Updated: (HADOOP-1216) Hadoop should support reduce none
 option
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     [ https://issues.apache.org/jira/browse/HADOOP-1216?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Runping Qi updated HADOOP-1216:
-------------------------------

    Status: Patch Available  (was: Open)

> Hadoop should support reduce none option
> ----------------------------------------
>
>                 Key: HADOOP-1216
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1216
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: mapred
>            Reporter: Runping Qi
>         Assigned To: Runping Qi
>         Attachments: patch_1216.txt
>
>
> This has been a highly desired feature in streaming world and was asked occationally in the non-streaming side.
> Streaming implemented a working (hacking) solution. But it also generates discrepency between hadoop 
> streaming/non-streaming model. It would be nice if Hadoop offers such a feature 
> that works both streaming and non-streaming. Owen and I discussed this a bit and here is the 
> general idea for further discussions/suggestions:
> 1. Allows the user to specify reducer=none in jobconf. 
> 2. The user still can specify output format and output directory
> 3. Each mapper will generate an output file in the specified directory. The naming convention can still be like part-xxxxxxxx
> where xxxxxxxx is the map task number.
> 4. The mapoutput collector of a mapper task will be a record writer on the 
> 5. The mapper will call output.collect() to write the output, thus the same mapper class can be 
> used, regardless reducer none is set or not.
> When reducer is set to none for a job, there will be no mapoutput files writen on to local file system at all, 
> and no data shuffling between mappers and reducers. As a mapper of fact, the framework may choose 
> not to create reducers at all.
>  

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