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Date: Tue, 23 Dec 2008 10:16:44 -0800 (PST)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Updated: (HADOOP-4927) Part files on the output filesystem
 are created irrespective of whether the corresponding task has anything to
 write there
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     [ https://issues.apache.org/jira/browse/HADOOP-4927?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tsz Wo (Nicholas), SZE updated HADOOP-4927:
-------------------------------------------

    Component/s: mapred
     Issue Type: Bug  (was: New Feature)

> I believe some users did mention that the feature of having exactly N output files is useful.

I also believe it is useful in some cases, especially when all output files are empty (ah, you may argue that the entire job is not useful in this case :) ).  However, it is costly to maintain empty files in HDFS and I believe it is USELESS in many cases.  Could we have an option for not creating them or cleaning them?

> Part files on the output filesystem are created irrespective of whether the corresponding task has anything to write there
> --------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-4927
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4927
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Devaraj Das
>             Fix For: 0.20.0
>
>
> When OutputFormat.getRecordWriter is invoked, a part file is created on the output filesystem. But the created RecordWriter is not used until the OutputCollector.collect call is made by the task (user's code). This results in empty part files even if the OutputCollector.collect is never invoked by the corresponding tasks.

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