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.
   */
  
  /**
   * Provides a core set of planner rules.
   *
   * <p>Consider this package to be the "standard library" of planner rules.
   * Most of the common rewrites that you would want to perform on logical
   * relational expressions, or generically on any data source, are present,
   * and have been well tested.
   *
   * <p>Of course, the library is never complete, and contributions are welcome.
   *
   * <p>Not present are rules specific to a particular data source: look in that
   * data source's adapter.
   *
   * <p>Also out of the scope of this package are rules that support a particular
   * operation, such as decorrelation or recognizing materialized views. Those are
   * defined along with the algorithm.
   *
   * <p>For
   *
   * <h2>Related packages and classes</h2>
   * <ul>
   *    <li>Package<code> <a href="../../sql/package-summary.html">
   *        org.apache.calcite.sql</a></code>
   *        is an object model for SQL expressions</li>
   *    <li>Package<code> <a href="../../rex/package-summary.html">
   *        org.apache.calcite.rex</a></code>
   *        is an object model for relational row expressions</li>
   *    <li>Package<code> <a href="../../plan/package-summary.html">
   *        org.apache.calcite.plan</a></code>
   *        provides an optimizer interface.</li>
   * </ul>
   */
  package org.apache.calcite.rel.rules;
  