FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -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. The transformed intermediate records do not need to be of the same type as the input records. A given input pair can map to zero or many output pairs.

Detailed explanation-2: -MapReduce Key value pair generation in Hadoop Key-value pair in MapReduce is generated as follows: InputSplit – It is the logical representation of data which InputFormat generates. In MapReduce program it describes a unit of work that contains a single map task. RecordReader – It communicates with the InputSplit.

Detailed explanation-3: -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-4: -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.