presto-main/src/main/java/io/prestosql/sql/planner/PlanFragmenter.java/FragmentProperties/setSingleNodeDistribution
class FragmentProperties:        public FragmentProperties setSingleNodeDistribution()
        {
            if (partitioningHandle.isPresent() && partitioningHandle.get().isSingleNode()) {
                // already single node distribution
                return this;
            }

            checkState(!partitioningHandle.isPresent(),
                    "Cannot overwrite partitioning with %s (currently set to %s)",
                    SINGLE_DISTRIBUTION,
                    partitioningHandle);

            partitioningHandle = Optional.of(SINGLE_DISTRIBUTION);

            return this;
        }