Hadoop Interview Question and Answers

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Hadoop Interview Questions
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• As Hadoop becomes the hot career today, many
  finds difficult to pass through interview.

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• In this post we have put together a comprehensive
  list of frequently asked interview questions and
  answers to help you get through your Hadoop
  interview.

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• 1) What is MapReduce?
• It is a framework or a programming model that is
  used for processing large data sets over clusters
  of computers using distributed programming.

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• 2) What are maps and reduces?
• Maps and Reduces are two phases of solving a
  query in HDFS. Map is responsible to read data
  from input location, and based on the input type,
  it will generate a key value pair, that is, an
  intermediate output in local machine. Reducer
  is responsible to process the intermediate output
  received from the mapper and generate the final
  output.

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• 3) What are the four basic parameters of a
  mapper?
• The four basic parameters of a mapper are Long
  Writable, text, text and IntWritable. The first
  two represent input parameters and the second two
  represent intermediate output parameters.

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• 4) What are the four basic parameters of a
  reducer?
• The four basic parameters of a reducer are text,
  IntWritable, text, IntWritable. The first two
  represent intermediate output parameters and the
  second two represent final output parameters.

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• 5) Which are the three modes in which Hadoop can
  be run?
• The three modes in which Hadoop can be run are
• 1. standalone (local) mode
• 2. Pseudo-distributed mode
• 3. Fully distributed mode

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• 6) What are the features of Stand alone (local)
  mode?
• In stand-alone mode there are no daemons,
  everything runs on a single JVM. It has no DFS
  and utilizes the local file system. Stand-alone
  mode is suitable only for running MapReduce
  programs during development. It is one of the
  most least used environments.

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• 7) What are the features of Pseudo mode?
• Pseudo mode is used both for development and in
  the QA environment. In the Pseudo mode all the
  daemons run on the same machine.

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• 8) What is BloomMapFile used for?
• The BloomMapFile is a class that extends MapFile.
  So its functionality is similar to MapFile.
  BloomMapFile uses dynamic Bloom filters to
  provide quick membership test for the keys. It is
  used in Hbase table format.

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• 9) What is PIG?
• PIG is a platform for analyzing large data sets
  that consist of high level language for
  expressing data analysis programs, coupled with
  infrastructure for evaluating these programs.
  PIGs infrastructure layer consists of a compiler
  that produces sequence of MapReduce Programs.

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• 10) What is the difference between logical and
  physical plans?
• The logical plan describes the logical operators
  that have to be executed by Pig during execution.
  After this, Pig produces a physical plan. The
  physical plan describes the physical operators
  that are needed to execute the script.

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• Weve covered some of the frequently asked
  interview questions.

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• If you are looking out for more Hadoop Interview
  Questions that are frequently asked by employers,
  visit
• http//www.edureka.in/blog/category/big-data-and-h
  adoop/