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Message-ID: <12067933.237811281376337208.JavaMail.jira@thor>
Date: Mon, 9 Aug 2010 13:52:17 -0400 (EDT)
From: "David Rosenstrauch (JIRA)" <jira@apache.org>
To: mapreduce-dev@hadoop.apache.org
Subject: [jira] Created: (MAPREDUCE-2001) Enhancement to
 SequenceFileOutputFormat to allow user to set MetaData
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Enhancement to SequenceFileOutputFormat to allow user to set MetaData
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                 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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