What Is A Identitymapper And Identityreducer In Mapreduce ?

1.	What Is A Identitymapper And Identityreducer In Mapreduce ?
Answer» org.apache.hadoop.mapred.lib.IdentityMapper Implements the IDENTITY FUNCTION, mapping inputs directly to outputs. If MapReduce programmer do not set the Mapper CLASS using JobConf.setMapperClass then IdentityMapper.class is used as a DEFAULT value. org.apache.hadoop.mapred.lib.IdentityReducer PERFORMS no reduction, writing all input values directly to the output. If MapReduce programmer do not set the Reducer Class using JobConf.setReducerClass then IdentityReducer.class is used as a default value.

Answer»

org.apache.hadoop.mapred.lib.IdentityMapper Implements the IDENTITY FUNCTION, mapping inputs directly to outputs. If MapReduce programmer do not set the Mapper CLASS using JobConf.setMapperClass then IdentityMapper.class is used as a DEFAULT value.
org.apache.hadoop.mapred.lib.IdentityReducer PERFORMS no reduction, writing all input values directly to the output. If MapReduce programmer do not set the Reducer Class using JobConf.setReducerClass then IdentityReducer.class is used as a default value.

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