#28: reduce VS reduceByKey in Apache Spark RDDs

reduce() and reduceByKey() are two distinct operations available in Apache Spark, a distributed computing framework for big data processing.

Reduce:

• reduce is an ACTION that collapses the elements of an RDD (Resilient Distributed Dataset) into a single result.
• It applies a function that takes two elements and returns a single element of the same type.
• The function should be associative and commutative, meaning it can be applied in any order.
• It operates on the entire RDD.

Example:

reduceByKey:

• reduceByKey is a TRANSFORMATION that combines values with the same key in a Pair RDD using a specified associative and commutative function.
• It operates on Pair RDDs, where each element is a key-value pair.
• It reduces values with the same key to a single value using the provided function.

Example:

• In this example, the values for each key are summed up.

In summary, while both reduce and reduceByKey perform reduction operations, reduce operates on the entire RDD, collapsing it to a single result, whereas reduceByKey works on Pair RDDs, reducing values with the same key to a single value.