In the reducer, the MapReduce API provides you with an iterator over Writable values. What does calling the next () method return?

The correct answer is C. It returns a reference to the same Writable object each time, but populated with different data. Calling Iterator.next() will always return the SAME EXACT instance of IntWritable, with the contents of that instance replaced with the next value.

Developing with Apache Spark Core

Question

Options

AIt returns a reference to a different Writable object time.
BIt returns a reference to a Writable object from an object pool.
CIt returns a reference to the same Writable object each time, but populated with different data.
DIt returns a reference to a Writable object. The API leaves unspecified whether this is a reused object
EIt returns a reference to the same Writable object if the next value is the same as the previous value,

How the community answered

(22 responses)

A
14% (3)
C
73% (16)
D
9% (2)
E
5% (1)

Explanation

Calling Iterator.next() will always return the SAME EXACT instance of IntWritable, with the contents of that instance replaced with the next value.

Topics

#reducer iterator#Writable reuse#next() method#object reference

Community Discussion

No community discussion yet for this question.

Full CCD-410 Practice