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 does 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 does 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 does 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 does not set the Reducer Class using JobConf.setReducerClass then IdentityReducer.class is used as a default value.

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