BDA_Unit2

Which of the following best describes the MapReduce programming model?

• Key-Value based parallel processing model

• Relational database querying model

• Event-driven programming model

• Object-oriented programming model

In MapReduce, the Map function:

• Combines the output of reducers

• Filters out unwanted keys

• Processes input data and produces intermediate key-value pairs

• Directly produces the final result

Which component in Hadoop is responsible for running MapReduce jobs?

• NameNode

• ResourceManager

• DataNode

• NodeManager

The Reduce function in MapReduce:

• Filters input data

• Merges intermediate values for the same key

• Reads data from HDFS and writes to Map function

• Stores metadata about the cluster

In MapReduce, the shuffle phase:

• Executes after the reduce function

• Sorts and transfers intermediate data between Map and Reduce

• Occurs before the map phase

• Cleans temporary storage

What is the default number of reducers if not specified?

• 0

• 1

• Equal to number of mappers

• Determined by block size

Which method in the Mapper class processes each key-value input?

• reduce()

• run()

• map()

• start()

The intermediate output of a Mapper is stored in:

• HDFS

• Local disk of the node

• NameNode memory

• Distributed cache

In a word count program, the key emitted by the Mapper is usually:

• The frequency of the word

• The entire line of text

• The word itself

• A document ID

What data structure is used for intermediate key-value storage in the shuffle phase?

• Stack

• Heap

• HashMap

• Array