presto-main/src/main/java/io/prestosql/operator/exchange/LocalExchangeSourceOperator.java/LocalExchangeSourceOperator/createOperator
class LocalExchangeSourceOperator:        @Override
        public Operator createOperator(DriverContext driverContext)
        {
            checkState(!closed, "Factory is already closed");

            LocalExchange inMemoryExchange = localExchangeFactory.getLocalExchange(driverContext.getLifespan());

            OperatorContext operatorContext = driverContext.addOperatorContext(operatorId, planNodeId, LocalExchangeSourceOperator.class.getSimpleName());
            return new LocalExchangeSourceOperator(operatorContext, inMemoryExchange.getNextSource());
        }