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CCD-410 · Question #51
What data does a Reducer reduce method process?
The correct answer is C. All data for a given key, regardless of which mapper(s) produced it. 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.
Hadoop Ecosystem Fundamentals
Question
What data does a Reducer reduce method process?
Options
- AAll the data in a single input file.
- BAll data produced by a single mapper.
- CAll data for a given key, regardless of which mapper(s) produced it.
- DAll data for a given value, regardless of which mapper(s) produced it.
How the community answered
(39 responses)- A18% (7)
- B8% (3)
- C69% (27)
- D5% (2)
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.
Topics
#MapReduce#Reducer#key grouping#reduce method
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