content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to you under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.calcite.rel.rules;
  
  /**
   * A rule that implements this interface indicates that the new RelNode
   * is typically better than the old one. All the substitution rules will
   * be executed first until they are done. The execution order of
   * substitution rules depends on the match order.
   */
  public interface SubstitutionRule extends TransformationRule {
  
    /**
     * Whether the planner should automatically prune old node when
     * there is at least 1 equivalent rel generated by the rule.
     *
     * <p>Default is false, the user needs to prune the old node
     * manually in the rule.
     */
    default boolean autoPruneOld() {
      return false;
    }
  }
  