What is the difference between a zero reducer and identity reducer in Hadoop Mapreduce

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I'm a newbie to Hadoop and Big Data Ecosystem. I want to know the difference between a zero and an identity reducer. Help needed.
Apr 10, 2018 in Big Data Hadoop by Ashish
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edited Apr 10, 2018 by Ashish 1,330 views

1 answer to this question.

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A Zero reducer as the name suggests omits the reducing step and the final output is only the map part of MapReduce. It is also known as a Map-only step.

As far as  Identity Reducer is concerned, the input Key, Value pairs are just dumped into the output as it is without any aggregation, except the data is sorted based on the key. Here, shuffle & sort happens except the aggregation. Hence, Identity Reducer is used if you only want to sort the input data from map output.
answered Apr 10, 2018 by kurt_cobain
• 9,390 points

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