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From "David Rosenstrauch (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-2001) Enhancement to SequenceFileOutputFormat to allow user to set MetaData
Date Mon, 09 Aug 2010 17:52:17 GMT
Enhancement to SequenceFileOutputFormat to allow user to set MetaData

                 Key: MAPREDUCE-2001
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2001
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
    Affects Versions: 0.20.2
            Reporter: David Rosenstrauch
            Priority: Minor

The org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat class currently does not
provide a way for the user to pass in a MetaData object to be written to the SequenceFile.

Currently he only way for a developer to implement this functionality appears to be to create
a subclass which overrides the SequenceFileOutputFormat's getRecordWriter() method, which
is a bit of a kludge.

This seems to be a common enough request to warrant a fix of some sort.  (It's already been
brought up twice in the past year:  http://www.mail-archive.com/common-user@hadoop.apache.org/msg02198.html
and http://www.mail-archive.com/mapreduce-user@hadoop.apache.org/msg00904.html)

A couple of possible solutions:

1) provide a static method SequenceFileOutputFormat.setMetaData(Job, MetaData)

2) Provide a (non-static) setMetaData() method on the SequenceFileOutputFormat class.  The
user would create a subclass of SequenceFileOutputFormat which, say, implements Configurable.
 Then in the setConf() method, the user could create the MetaData object (using data from
the Configuration), and then call setMetaData.  The SequenceFileOutputFormat would then use
this MetaData object when creating the SequenceFile.  (Note that the user would have to create
a subclass of SequenceFileOutputFormat to make this solution work.)

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