How to define MapReduce mapping

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Define

Map: commonly known as mapping. The number of elements remains unchanged after map.

Such as:

X-- > (xPhone1)

Y-- > (yPhone1)

Z-- > (zPhone1)

Reduce: commonly known as the specification, the number of elements after reduce (xPhone1)

X-- > (xPhone1)-- > > (xPhone1 / 1 / 1)

X-- > (xPhone1)

MapReduce architecture

Workflow for MR job submission to Yarn = = Yarn architecture design = = Yarn workflow

Shuffle

Map- > shuffle- > reduce

Understanding: the same elements of key are put together through the network IO for business calculation.

Common command

Mapred

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