Hadoop Reducer – Configuration

If we dont set the number of reducer tasks in our driver class, then by default, it will be assumed as 1 and run the job.

If we dont set the reducer class in our driver class,then the IdentityReducer will be taken by default and it will just do sorting and shuffling and produce the results in a single output file.

If we set the number of reducer tasks as 0, then no reducer tasks will be run and the map output will be the final output and would be written into HDFS.