Why MapReduce uses the key-value pair to process the data?
MapReduce works on unstructured and semi-structured data apart from structured data. One can read the Structured data like the ones stored in RDBMS by columns. But handling unstructured data is feasible using key-value pairs. And the very core idea of MapReduce work on the basis of these pairs. Framework map data into a collection of key-value pairs by mapper and reducer on all the pairs with the same key. So as stated by Google themselves in their research publication. In most of the computations-
Map operation applies on each logical “record” in our input. This computes a set of intermediate key-value pairs. Then apply reduce operation on all the values that share the same key. This combines the derived data properly.
In conclusion, we can say that key-value pairs are the best solution to work on data problems on MapReduce.
