Database Reference
In-Depth Information
In the preceding diagram, you see a very simple flow of MapReduce. However, in real
production scenarios, there are multiple mappers and reducers.
When there are multiple mappers and reducers involved, there is a phase between the
mapper and reducer known as the
shuffle and sort
phase. In this phase, all the keys are
sorted and sent to the reducers. Each reducer works on the set of keys and values provided
as input and generates their own output file as shown in the following diagram:
