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Reducer 1 question

Explorer

I  have seen  some of my jobs are using only  one reducer in the end.  Does it mean we have one output file?  Or it depends?

1 REPLY 1

Expert Contributor

Hi,

 

The Reducer process the output of the mapper. After processing the data, it produces a new set of output. At last HDFS stores this output data. Reducer takes a set of an intermediate key value pair produced by the mapper as the input and runs a Reducer function on each of them.

The mappers and reducers depends on the data that is processing.

 

You can manually set the number of reducers with below property but i think it is not recommended.

set mapred.reduce.tasks=xx;

 

Regards,

Chethan YM

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