identityreducer in the new Hadoop API

Question

I spent almost a day but couldn't figure out how to use IdentityReducer in the new Hadoop API. All references or classes I can find are with the old API. And obviously mixing up old API idetntitreducer class in the new API codebase doesn't go well. Any help will be appreciated.

Just to add a bit more detail: import org.apache.hadoop.mapred.lib.IdentityReducer is what I can find wherever I look but this isn't a new API class. — kee, Mar 17 '12 at 03:16

score 37 · Accepted Answer · answered Mar 17 '12 at 10:28

37

Mainly because in the new API Mapper and Reducer are classes instead of interfaces, they are the new replacement of IdentityMapper/Reducer.

So you just have to use Mapper.class and Reducer.class to get the identity.

answered Mar 17 '12 at 10:28

Thomas Jungblut

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And if you don't explicitly set the mapper or reducer class, the identity version is used by default – Chris White Mar 22 '12 at 01:36

vpap · Answer 2 · 2012-08-20T09:33:41.907

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Hadoop Streaming - Hadoop 1.0.2

According to this, the command is

-x org.apache.hadoop.mapred.lib.IdentityX

where x = mapper or reducer and X = Mapper or Reducer respectively.

I tested myself and works.

edited Aug 20 '12 at 09:33

answered Aug 20 '12 at 09:21

vpap

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score 0 · Answer 3 · answered Mar 17 '12 at 03:32

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Have a look :

http://hadoop.apache.org/common/docs/r1.0.0/api/org/apache/hadoop/mapred/lib/IdentityReducer.html

Its for hadoop stable version

answered Mar 17 '12 at 03:32

Mohyt

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identityreducer in the new Hadoop API

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