Answer / Shekher Raghuvanshi

In MapReduce, the map function takes input data (key-value pairs) and performs a mapping operation to produce intermediate key-value pairs. The reduce function then takes these intermediate key-value pairs, groups them by key, and performs a reduction operation to produce the final output. The main difference is that the map function processes data in parallel, while the reduce function aggregates the results of the map function.

How to specify more than one directory as input to the MapReduce Job?

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If reducers do not start before all mappers finish then why does the progress on mapreduce job shows something like map(50%) reduce(10%)? Why reducers progress percentage is displayed when mapper is not finished yet?

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In MapReduce Data Flow, when Combiner is called?

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In Hadoop, which file controls reporting in Hadoop?

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What is identity mapper and identity reducer?

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What are the four basic parameters of a reducer?

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What are the advantages of using map side join in mapreduce?

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what is distributed cache in mapreduce framework?

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With the help of two examples name the map and reduce function purpose

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Explain about the partitioning, shuffle and sort phase

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Mention what is the hadoop mapreduce apis contract for a key and value class?

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A number of combiners can be changed or not in MapReduce?

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