presto-main/src/main/java/io/prestosql/cost/CostCalculatorUsingExchanges.java/CostCalculatorUsingExchanges/visitOutput
class CostCalculatorUsingExchanges:        @Override
        public PlanCostEstimate visitOutput(OutputNode node, Void context)
        {
            return costForStreaming(node, LocalCostEstimate.zero());
        }