When my tuple type includes a generic type parameter, the pair RDD functions aren't available. Take for example the following (a join on two RDDs, taking the sum of the values):

def joinTest(rddA: RDD[(String, Int)], rddB: RDD[(String, Int)]) : RDD[(String, Int)] = {
    rddA.join(rddB).map { case (k, (a, b)) => (k, a+b) }
}


That works fine, but lets say I replace the type of the key with a generic type:

def joinTest[K](rddA: RDD[(K, Int)], rddB: RDD[(K, Int)]) : RDD[(K, Int)] = {
    rddA.join(rddB).map { case (k, (a, b)) => (k, a+b) }
}


This latter function gets the compiler error "value join is not a member of org.apache.spark.rdd.RDD[(K, Int)]".

The reason is probably obvious, but I don't have much Scala experience. Can anyone explain what I'm doing wrong?

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Daniel Siegmann, Software Developer
Velos
Accelerating Machine Learning

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