Mapr (HP) Hadoop Developer Certification Questions and Answers (Dumps and Practice Questions)

Question : Select correct statement regarding combiner?



1. Use combiner, while doing aggregation and if number of keys is significantly less than the number of records after map phase.

2. Combiner can be called multiple times on Same Mapper Task node

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4. 1,2

5. 1,2,3


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Explanation:




Question : Which is true regarding Combiner configuration and creation



1. Combiner can be set in Driver class

2. Combiner must implement combine() method

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4. 1,3

5. 1,2,3


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Explanation: The Combiner class is used in between the Map class and the Reduce class to reduce the volume of data transfer between Map and
Reduce. Usually, the output of the map task is large and the data transferred to the reduce task is high

A combiner does not have a predefined interface and it must implement the Reducer interface s reduce() method.

A combiner operates on each map output key. It must have the same output key-value types as the Reducer class.

A combiner can produce summary information from a large dataset because it replaces the original Map output.

job.setCombinerClass(MyReducer.class);





Question : How can Map output compression, improves the performance of Hadoop Job ?



1. It reduces Disk I/O

2. It reduces CPU cycle

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4. It always uses ZLIB codec.


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Explanation: When you use compression for output of the Map tasks. It will reduce the Disk I/O and network I/O , because lesser data needs to be
stored on local disk or needs to transferred over the network. ZLIB is a good codec for Compression , but it can not be always used as it needs more CPU.
Output of Map tasks is always written to local disk.

Related Questions

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Question : Which of the following is/are responsibilities of InputFormat?



1. Validate the input files and directories that exist for the job

2. Split the input files into InputSplits

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4. 1,2

5. 1,2,3



Question : Select the correct statement regarding input split and block size



1. input split may be smaller the block size

2. input split may be larger the block size

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4. 1,2
5. 1,2,3


Question : Which of the following are the methods available in a InputFormat class and needs to be implemented?



1. getSplits()

2. createRecordReader()

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4. 1,2

5. 1,2,3



Question : When you change the size of inputSplit with configuration, what would be impact?



1. It will change number of reducer for a particular job processing this file.

2. It will change number of mapper for a particular job processing this file.

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4. 1,2

5. 1,2,3



Question : Select correct statement regarding inputSplit



1. Last record of inputsplit will always be a complete record

2. Last record of inputsplit may be complete or incomplete

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4. 1,2

5. 1,2,3



Question : What is the purpose of "CombineFileSplit" ?



1. combines multiple files into a single split

2. combines multiple splits into a single split

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4. 1,2

5. 1,2,3