presto-main/src/main/java/io/prestosql/operator/DistinctLimitOperator.java/DistinctLimitOperatorFactory/createOperator
class DistinctLimitOperatorFactory:        @Override
        public Operator createOperator(DriverContext driverContext)
        {
            checkState(!closed, "Factory is already closed");
            OperatorContext operatorContext = driverContext.addOperatorContext(operatorId, planNodeId, DistinctLimitOperator.class.getSimpleName());
            List<Type> distinctTypes = distinctChannels.stream()
                    .map(sourceTypes::get)
                    .collect(toImmutableList());
            return new DistinctLimitOperator(operatorContext, distinctChannels, distinctTypes, limit, hashChannel, joinCompiler);
        }