reactor-core/src/main/java/reactor/core/publisher/ParallelFlux.java
public final Flux<T> ordered(Comparator<? super T> comparator, int prefetch) {
		return new ParallelMergeOrdered<>(this, prefetch, Queues.get(prefetch), comparator);
	}
public final Flux<T> ordered(Comparator<? super T> comparator, int prefetch) {
		return new ParallelMergeOrdered<>(this, prefetch, Queues.get(prefetch), comparator);
	}
Merges the values from each 'rail', but choose which one to merge by way of a
provided {@link Comparator}, picking the smallest of all rails. The result is
exposed back as a {@link Flux}.

@param comparator the comparator to choose the smallest value available from all rails
@param prefetch the prefetch to use
@return the new Flux instance

@see ParallelFlux#ordered(Comparator)