presto-main/src/main/java/io/prestosql/operator/exchange/LocalMergeSourceOperator.java/LocalMergeSourceOperatorFactory/LocalMergeSourceOperatorFactory
class LocalMergeSourceOperatorFactory:        public LocalMergeSourceOperatorFactory(
                int operatorId,
                PlanNodeId planNodeId,
                LocalExchangeFactory localExchangeFactory,
                List<Type> types,
                OrderingCompiler orderingCompiler,
                List<Integer> sortChannels,
                List<SortOrder> orderings)
        {
            this.operatorId = operatorId;
            this.planNodeId = requireNonNull(planNodeId, "planNodeId is null");
            this.localExchangeFactory = requireNonNull(localExchangeFactory, "exchange is null");
            this.types = ImmutableList.copyOf(requireNonNull(types, "types is null"));
            this.orderingCompiler = requireNonNull(orderingCompiler, "orderingCompiler is null");
            this.sortChannels = ImmutableList.copyOf(requireNonNull(sortChannels, "sortChannels is null"));
            this.orderings = ImmutableList.copyOf(requireNonNull(orderings, "orderings is null"));
        }