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From Aaron Kimball <aa...@cloudera.com>
Subject Re: Partitioned Datasets Map/Reduce
Date Mon, 05 Jul 2010 07:51:44 GMT
One possibility: write out all the partition numbers (one per line) to a
single file, then use the NLineInputFormat to make each line its own map
task. Then in your mapper itself, you will get in a key of "0" or "1" or "2"
etc. Then explicitly open /dataset1/part-(n) and /dataset2/part-(n) in your

If you wanted to be more clever, it might be possible to subclass
MultiFileInputFormat to group together both datasets "file-number-wise" when
generating splits, but I don't have specific guidance here.

- Aaron

On Sat, Jul 3, 2010 at 9:35 AM, abc xyz <fabc_xyz111@yahoo.com> wrote:

> Hello everyone,
> I have written my custom partitioner for partitioning datasets. I want  to
> partition two datasets using the same partitioner and then in the  next
> mapreduce job, I want each mapper to handle the same partition from  the
> two
> sources and perform some function such as joining etc. How I  can I ensure
> that
> one mapper gets the split that corresponds to same  partition from both the
> sources?
> Any help would be highly appreciated.

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