presto-main/src/main/java/io/prestosql/sql/planner/LocalExecutionPlanner.java/LocalExecutionPlanner/visitAssignUniqueId
class LocalExecutionPlanner:        @Override
        public PhysicalOperation visitAssignUniqueId(AssignUniqueId node, LocalExecutionPlanContext context)
        {
            PhysicalOperation source = node.getSource().accept(this, context);

            OperatorFactory operatorFactory = new AssignUniqueIdOperator.AssignUniqueIdOperatorFactory(
                    context.getNextOperatorId(),
                    node.getId());
            return new PhysicalOperation(operatorFactory, makeLayout(node), context, source);
        }