presto-main/src/main/java/io/prestosql/sql/planner/PlanFragmenter.java/PlanFragmenter/isCompatibleSystemPartitioning
class PlanFragmenter:        private boolean isCompatibleSystemPartitioning(PartitioningHandle distribution)
        {
            ConnectorPartitioningHandle currentHandle = partitioningHandle.get().getConnectorHandle();
            ConnectorPartitioningHandle distributionHandle = distribution.getConnectorHandle();
            if ((currentHandle instanceof SystemPartitioningHandle) &&
                    (distributionHandle instanceof SystemPartitioningHandle)) {
                return ((SystemPartitioningHandle) currentHandle).getPartitioning() ==
                        ((SystemPartitioningHandle) distributionHandle).getPartitioning();
            }
            return false;
        }