CCD-410 · Question #9
CCD-410 Question #9: Real Exam Question with Answer & Explanation
The correct answer is A. Yes, because the sum operation is both associative and commutative and the input and output types. Combiners are used to increase the efficiency of a MapReduce program. They are used to aggregate intermediate map output locally on individual mapper outputs. Combiners can help you reduce the amount of data that needs to be transferred across to the You can use your reducer code
Question
Options
- AYes, because the sum operation is both associative and commutative and the input and output types
- BNo, because the sum operation in the reducer is incompatible with the operation of a Combiner.
- CNo, because the Reducer and Combiner are separate interfaces.
- DNo, because the Combiner is incompatible with a mapper which doesn't use the same data type for
- EYes, because Java is a polymorphic object-oriented language and thus reducer code can be reused
Explanation
Combiners are used to increase the efficiency of a MapReduce program. They are used to aggregate intermediate map output locally on individual mapper outputs. Combiners can help you reduce the amount of data that needs to be transferred across to the You can use your reducer code as a combiner if the operation performed is commutative and The execution of combiner is not guaranteed, Hadoop may or may not execute a combiner. Also, if required it may execute it more then 1 times. Therefore your MapReduce jobs should not depend on the combiners execution.
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