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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4927) Part files on the output filesystem are created irrespective of whether the corresponding task has anything to write there
Date Thu, 05 Feb 2009 18:43:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12670855#action_12670855
] 

Doug Cutting commented on HADOOP-4927:
--------------------------------------

 - LazyOutputFormat should keep a field for the nested output format, not create it again
for each call, no?
 - We might implement generic FilterOutputFormat and FilterRecordReader that LazyOutputFormat
and LazyRecordReader extend.  This is probably not the last time someone will need to wrap
an OutputFormat or a RecordReader.
 - JobConf#setOutputFormatClass(Class, boolean) should instead be static LazyOutputFormat#setClass(Job,
Class, boolean).  This localizes the change, and it's still a one-line change for applications.
 - Similarly, JobContext#getLazyOutputFormatClass() should instead be static LazyOutputFormat#getClass(JobContext).
 This feature can be entirely contained in LazyOutputFormat and should not require changes
to the kernel.

> 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: New Feature
>          Components: mapred
>            Reporter: Devaraj Das
>            Assignee: Jothi Padmanabhan
>             Fix For: 0.21.0
>
>         Attachments: hadoop-4927-v1.patch, hadoop-4927-v2.patch, hadoop-4927-v3.patch,
hadoop-4927.patch
>
>
> 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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