DATABASE FUNDAMENTALS
BASICS OF BIG DATA
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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shuffling
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secondary sorting
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forking
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reducing
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Detailed explanation-1: -In MapReduce data processing flow output of mapper is written on local disk whereas output of reducer is written on hdfs.
Detailed explanation-2: -9) Where is Mapper output stored? The intermediate key value data of the mapper output will be stored on local file system of the mapper nodes. This directory location is set in the config file by the Hadoop Admin.
Detailed explanation-3: -Shuffle phase in Hadoop transfers the map output from Mapper to a Reducer in MapReduce. Sort phase in MapReduce covers the merging and sorting of map outputs. Data from the mapper are grouped by the key, split among reducers and sorted by the key. Every reducer obtains all values associated with the same key.
Detailed explanation-4: -7. Which of the following phases occur simultaneously? Explanation: The shuffle and sort phases occur simultaneously; while map-outputs are being fetched they are merged.