FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -MapReduce is a programming model for processing and generating large data sets. Users specify a map function that processes a key/value pair to generate a set of intermediate key/value pairs, and a reduce function that merges all intermediate values associated with the same intermediate key.

Detailed explanation-2: -Mapper. Mapper maps input key-value pairs to a set of intermediate key-value pairs. Maps are the individual tasks that transform input records into intermediate records.

Detailed explanation-3: -RecordReader – It communicates with the InputSplit and it converts the Split into records which are in form of key-value pairs that are suitable for reading by the mapper. By default, RecordReader uses TextInputFormat for converting data into a key-value pair.

Detailed explanation-4: -Mapper produces the intermediate key values pairs and these are read by reducer. Data corresponding to same key is grouped together and after some processing final output will be produced in the form of key value pairs.

Detailed explanation-5: -Intermediate Keys − They key-value pairs generated by the mapper are known as intermediate keys. Combiner − A combiner is a type of local Reducer that groups similar data from the map phase into identifiable sets.