Method register

core/src/main/java/org/apache/calcite/rel/RelNode.java:390–390

Registers any special rules specific to this kind of relational expression. The planner calls this method this first time that it sees a relational expression of this class. The derived class should call org.apache.calcite.plan.RelOptPlanner#addRule for each rule, and then call {@code su

(RelOptPlanner planner)

   *                expressions
   */
  void register(RelOptPlanner planner);

  /**
   * Indicates whether it is an enforcer operator, e.g. PhysicalSort,