presto-main/src/main/java/io/prestosql/sql/planner/plan/ExchangeNode.java/ExchangeNode/roundRobinExchange
class ExchangeNode:    public static ExchangeNode roundRobinExchange(PlanNodeId id, Scope scope, PlanNode child)
    {
        return partitionedExchange(
                id,
                scope,
                child,
                new PartitioningScheme(Partitioning.create(FIXED_ARBITRARY_DISTRIBUTION, ImmutableList.of()), child.getOutputSymbols()));
    }