presto-main/src/main/java/io/prestosql/cost/CostCalculatorUsingExchanges.java/CostCalculatorUsingExchanges/calculateJoinOutputCost
class CostCalculatorUsingExchanges:        private LocalCostEstimate calculateJoinOutputCost(PlanNode join)
        {
            PlanNodeStatsEstimate outputStats = getStats(join);
            double joinOutputSize = outputStats.getOutputSizeInBytes(join.getOutputSymbols(), types);
            return LocalCostEstimate.ofCpu(joinOutputSize);
        }