[ http://issues.apache.org/jira/browse/HADOOP-115?page=all ]
Doug Cutting resolved HADOOP-115:
---------------------------------
Fix Version: 0.3
Resolution: Fixed
Your patch has some strange formatting, and some spurious whitespace changes.
I fixed most of these. It would also be best to have a unit test that uses
this feature. But I'm tired of this issue, and it should do no harm, so I
committed it.
> permit reduce input types to differ from reduce output types
> ------------------------------------------------------------
>
> Key: HADOOP-115
> URL: http://issues.apache.org/jira/browse/HADOOP-115
> Project: Hadoop
> Type: New Feature
> Components: mapred
> Reporter: Runping Qi
> Assignee: Runping Qi
> Fix For: 0.3
> Attachments: hadoop-115_ReduceTask.patch, hadoop-115_tk.patch,
> patch_115.txt.2006_05_16
>
> When map tasks write intermediate data out, they always use SequencialFile
> RecordWriter with key/value classes from the job object.
> When the reducers write the final results out, its output format is obtained
> from the job object. By default, it is TextOutputFormat, and no conflicts.
> However, if one wants to use SequencialFileFormat for the final results, then
> the key/value classes are also obtained from the job object, the same as the
> map tasks' output. Now we have a problem. It is impossible for the map
> outputs and reducer outputs use different key/value classes, if one wants the
> reducers generate outputs in SequentialFileFormat.
> A simple fix would be to add another two attributes to JobConf class:
> mapOutputLeyClass and mapOutputValueClass. That allows the user to have
> different key/value classes for the intermediate and final outputs.
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