for (int i = 0; i < layout.size(); i++) {
outputMappings.put(layout.get(i), new Input(i, 0));
}
// add exchange source as first operator in the current context
OperatorFactory factory = new InMemoryExchangeSourceOperatorFactory(context.getNextOperatorId(), exchange);
return new PhysicalOperation(factory, outputMappings.build());
}