Category: Big Data Technology

How are keys and values presented and passed to the reducers during a standard sort and shuffle phase of MapReduce?

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How are keys and values presented and passed to the reducers during a standard sort and shuffle phase of MapReduce?
Keys are presented to reducer in sorted order; values for a given key are not sorted.
Excellent ! Your Answer is Correct.
Keys are presented to reducer in sorted order; values for a given key are sorted in ascending order.
Keys are presented to a reducer in random order; values for a given key are not sorted.
Keys are presented to a reducer in random order; values for a given key are sorted in ascending order.

When is the earliest point at which the reduce method of a given Reducer can be called?

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When is the earliest point at which the reduce method of a given Reducer can be called?
Not until all mappers have finished processing all records.
Excellent ! Your Answer is Correct.
As soon as a mapper has emitted at least one record.
As soon as at least one mapper has finished processing its input split.
It depends on the InputFormat used for the job.
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