What data does a Reducer reduce method process?
A.
All the data in a single input file.
B.
All data produced by a single mapper.
C.
All data for a given key, regardless of which mapper(s) produced it.
D.
All data for a given value, regardless of which mapper(s) produced it.
Explanation:
Reducing lets you aggregate values together. A reducer function receives an iterator
of input values from an input list. It then combines these values together, returning a single output
value.
All values with the same key are presented to a single reduce task.
Reference: Yahoo! Hadoop Tutorial, Module 4: MapReduce
C.
All data for a given key, regardless of which mapper(s) produced it.
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0
C
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