Performing MapReduce operations

MapReduce is the programming model to perform operations (mainly aggregation) on distributed sets of data across various clusters in different servers. This concept was coined by Google and was used in the Google file system initially and later was adopted by the open source Hadoop project.

MapReduce works by processing the data on each server and then combine it together to form a result set. It actually divides into two operations namely Map and Reduce.

• Map: This performs the transformation of the elements in the group or individual sequence

• Reduce: This performs the aggregation and combines the results from Map into a meaningful result set

In RethinkDB, MapReduce queries operate in three steps as follows:

• Group operation: To process the data into groups. This step is optional

• Map operation: To transform the data or group of data into a sequence

• Reduce operation: To aggregate the sequence data to form a resultset

So mainly it is a Group MapReduce (GMR) operation...