/**
* Creates a new node with a single input for the optimizer plan.
*
* @param programOperator The PACT that the node represents.
*/
protected SingleInputNode(SingleInputOperator<?, ?, ?> programOperator) {
super(programOperator);
int[] k = programOperator.getKeyColumns(0);
this.keys = k == null || k.length == 0 ? null : new FieldSet(k);
}
