Question

Which statement is true about the Combiner phase of the MapReduce architecture?

A. It determines the size and distribution of data split in the Map phase.
B. It reduces the amount of data that is sent to the Reducer task nodes.
C. It aggregates all input data before it goes through the Map phase.
D. It is performed after the Reducer phase to produce the final output.

Answer 1

The statement that the Combiner phase of the MapReduce architecture reduces the amount of data sent to the Reducer nodes is true. It functions as a mini-reducer, processing data on the same nodes as the Map tasks to decrease network load before the final Reduce phase.

Step-by-step explanation:

The true statement about the Combiner phase of the MapReduce architecture is: B. It reduces the amount of data that is sent to the Reducer task nodes. The Combiner is an optional phase that takes place after the Map phase and before the Reduce phase. It acts as a mini-reducer and processes the output of the Map phase on the same node where the Map task ran, thus reducing the amount of data transferred across the network to the Reducer nodes. This is particularly useful when performing operations like counting or summing, where the data can be partially combined before the final Reduce phase.