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Hadoop, mail # dev - MapReduce V1 vs MapReduce V2


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MapReduce V1 vs MapReduce V2
Matt Fellows 2014-01-03, 10:19
I'm thoroughly confused about which API is the recent one, which is the old
one and which method I should be using to write MapReduce applications.

I'm under the impression that MRv2 is primarily driven by the
org.apache.hadoop.mapreduce.* packages and MRv1 is primarily driven by the
org.apache.hadoop.mapred.* packages.

I've been led to believe that MRv2 applications extend MapReduceBase and
implement Mapper, Reducer etc.
and conversely the MRv1 applications extend Mapper, Reducer directly.

However I can not find a canonical statement to back any of this up.
 What's more I keep finding conflicting statements about these, such as
"'Hadoop - the definitive guide' gives example in MRv2 format" but then I
look at the examples and they use org.apache.hadoop.mapreduce.* packages,
but extend Mapper and extend Reducer, not MapReduceBase...

Can someone either point me at a canonical resource or just confirm / deny
my assumptions?

Kind regards

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