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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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postedDec 22, '08 at 6:01a
activeFeb 23, '09 at 3:19p

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