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CCD-410 · Question #52

All keys used for intermediate output from mappers must:

The correct answer is C. Implement WritableComparable. The MapReduce framework operates exclusively on <key, value> pairs, that is, the framework views the input to the job as a set of <key, value> pairs and produces a set of <key, value> pairs as the output of the job, conceivably of different types. The key and value classes have…

Hadoop Ecosystem Fundamentals

Question

All keys used for intermediate output from mappers must:

Options

  • AImplement a splittable compression algorithm.
  • BBe a subclass of FileInputFormat.
  • CImplement WritableComparable.
  • DOverride isSplitable.
  • EImplement a comparator for speedy sorting.

How the community answered

(22 responses)
  • B
    5% (1)
  • C
    77% (17)
  • D
    5% (1)
  • E
    14% (3)

Explanation

The MapReduce framework operates exclusively on <key, value> pairs, that is, the framework views the input to the job as a set of <key, value> pairs and produces a set of <key, value> pairs as the output of the job, conceivably of different types. The key and value classes have to be serializable by the framework and hence need to implement the Writable interface. Additionally, the key classes have to implement the WritableComparable interface to facilitate sorting by the

Topics

#MapReduce#WritableComparable#intermediate keys#serialization

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