src/main/java/com/googlecode/objectify/impl/LoadEngine.java
public void execute() {
		if (round.needsExecution()) {
			Round old = round;
			round = old.next();
			old.execute();
		}
	}
public void execute() {
		if (round.needsExecution()) {
			Round old = round;
			round = old.next();
			old.execute();
		}
	}
Starts asychronous fetching of the batch.