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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 Tue, 03 Feb 2009 17:41:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12670028#action_12670028
] 

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

> Unless there's a non-FileOutputFormat use case [ ... ]

I see Chris's point and agree.  Unless there's a strong reason to put features in the kernel
we should prefer to put them in library code, keeping the kernel minimal.  Are there non-FileInputFormats
that need this feature?

A wrapper implementation is a bit harder to use, since folks would need to both set the job's
outputformat to the wrapper, and set the wrapper's parameter to the real output format: two
changes instead of just setting a single parameter, although it is more generic.  We could
perhaps implement both: a flag for FileOutputFormat and a wrapper OutputFormat for folks who've
not subclassed FileOutputFormat?


> 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.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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