MutablePair (core/src/main/scala/org/apache/spark/util/MutablePair.scala)
- minimizes object allocation for tuple2.
case class MutablePair[@specialized(Int, Long, Double, Char, Boolean) T1,
@specialized(Int, Long, Double, Char, Boolean) T2]
(var _1: T1, var _2: T2) extends Product[T1, T2]
- specialized annotation is used to tell compiler to generate special classes for these types, where Boxing is avoided. see this for more info.
def this() = this(null.asInstanceOf[T1], null.asInstanceOf[T2])
- serialization requires a no-arg constructor. (for first non-serializable parent class)
usage example from spark sql:
rdd.mapPartitions { iter =>
val getPartitionKey = getPartitionKeyExtractor()
val mutablePair = new MutablePair[Int, InternalRow]()
iter.map { row => mutablePair.update(part.getPartition(getPartitionKey(row)), row) }
}
