Question - What are the two main phases of a MapReduce operation?
Answer -
A MapReduce operation can be divided into the following two primary phases:
- Map phase. MapReduce processes the input data, splits it into chunks and maps those chunks in preparation for analysis. MapReduce runs these processes in parallel.
- Reduce phase. MapReduce processes the mapped chunks, aggregating the data based on the defined logic. The output of these phases is then written to HDFS.
MapReduce operations are sometimes divided into phases other than these two. For example, the Reduce phase might be split into the Shuffle phase and the Reduce phase. In some cases, you might also see a Combiner phase, which is an optional phase used to optimize MapReduce operations.