Why isn't there a sortBy method in ParSeq despite that there is one in Seq?

Question

I have this simple query to run and I want to parallelize it:

val res : Array[Int] = valuesRand
.groupBy(v => v)
.toSeq
.sortBy(_._1)
.map(_._2.size)
.toArray

Is the following the performant equivalent of my query?

val res : Array[Int] = valuesRand
.par
.groupBy(v => v)
.par
.toIndexedSeq
.sortBy(_._1)
.map(_._2.size)
.toArray

I am asking that, because I couldn't find the sortBy method into ParSeq, although it exists in Seq.

Answer 1

The ParSeq class does not directly extend SeqLike which provides for the sortBy. You can see this from the definition of ParSeqLike:

trait ParSeqLike[+T, +Repr <: ParSeq[T], +Sequential <: scala.Seq[T] with SeqLike[T, Sequential]] extends GenSeqLike[T, Repr] with ParIterableLike[T, Repr, Sequential]

which ParSeq extends via

ParSeqLike[T, ParSeq[T], scala.Seq[T]]

Hence, only the Splitter in the underlying implementation is able to do a sortBy which does not help you one bit.