Apache Spark is the the elephant in a room full of data processing engines, yet Spark does not supply a foldLeft() or foldRight() method on its RDD class. Strange right? Such a fundamental collection method. How could it be forgotten? Or, was this not an accident? scoreAverageByPlayer(), which would take an RDD, and return an RDD … Continue reading Why Spark can’t foldLeft: Monoids and Associativity.