Answer / Varun Tomar

Partitioner in Hadoop is a component responsible for partitioning the data based on a specific key. The default partitioner in Hadoop is the HashPartitioner, which partitions data based on the hash value of the key. When a MapReduce job runs, the partitioner determines which parts of the data should be assigned to which reducer. The partitioner runs on the JobTracker/ResourceManager node in Hadoop 1 and on the YARN ResourceManager in Hadoop 2.

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