Javadoc
Clears internal states, must be called after getReadables().
Concretely, this clears the huge list of input splits held by objects like BeamBoundedSourceVertex before
sending the vertex to remote executors.
Between clearing states of an existing vertex, and creating a new vertex, we've chosen the former approach
to ensure consistent use of the same IRVertex object across the compiler, the master, and the executors.