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.tools;
  
  import org.apache.calcite.plan.RelOptLattice;
  import org.apache.calcite.plan.RelOptMaterialization;
  import org.apache.calcite.plan.RelOptPlanner;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  
  import java.util.List;
  
  /**
   * Program that transforms a relational expression into another relational
   * expression.
   *
   * <p>A planner is a sequence of programs, each of which is sometimes called
   * a "phase".
   *
   * <p>The most typical program is an invocation of the volcano planner with a
   * particular {@link org.apache.calcite.tools.RuleSet}.
   */
  public interface Program {
    RelNode run(RelOptPlanner planner, RelNode rel,
        RelTraitSet requiredOutputTraits,
        List<RelOptMaterialization> materializations,
        List<RelOptLattice> lattices);
  }
  