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;
  
  import org.apache.calcite.plan.RelOptRuleCall;
  import org.apache.calcite.plan.RelOptUtil;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.rel.core.Project;
  import org.apache.calcite.rel.logical.LogicalProject;
  import org.apache.calcite.tools.RelBuilder;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import org.immutables.value.Value;
  
  /**
   * Planner rule that pushes
   * {@link org.apache.calcite.rel.core.Project}
   * into a {@link MultiJoin},
   * creating a richer {@code MultiJoin}.
   *
   * @see org.apache.calcite.rel.rules.FilterMultiJoinMergeRule
   * @see CoreRules#PROJECT_MULTI_JOIN_MERGE
   */
  @Value.Enclosing
  public class ProjectMultiJoinMergeRule
      extends RelRule<ProjectMultiJoinMergeRule.Config>
      implements TransformationRule {
  
    /** Creates a ProjectMultiJoinMergeRule. */
    protected ProjectMultiJoinMergeRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public ProjectMultiJoinMergeRule(RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class));
    }
  
    @Deprecated // to be removed before 2.0
    public ProjectMultiJoinMergeRule(Class<? extends Project> projectClass,
        RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class)
          .withOperandFor(projectClass, MultiJoin.class));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      Project project = call.rel(0);
      MultiJoin multiJoin = call.rel(1);
  
      // if all inputs have their projFields set, then projection information
      // has already been pushed into each input
      boolean allSet = true;
      for (int i = 0; i < multiJoin.getInputs().size(); i++) {
        if (multiJoin.getProjFields().get(i) == null) {
          allSet = false;
          break;
        }
      }
      if (allSet) {
        return;
      }
  
      // create a new MultiJoin that reflects the columns in the projection
      // above the MultiJoin
      final RelBuilder relBuilder = call.builder();
      MultiJoin newMultiJoin =
          RelOptUtil.projectMultiJoin(multiJoin, project);
      relBuilder.push(newMultiJoin)
          .project(project.getProjects(), project.getRowType().getFieldNames());
  
      call.transformTo(relBuilder.build());
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableProjectMultiJoinMergeRule.Config.of()
          .withOperandFor(LogicalProject.class, MultiJoin.class);
  
      @Override default ProjectMultiJoinMergeRule toRule() {
        return new ProjectMultiJoinMergeRule(this);
      }
  
      /** Defines an operand tree for the given classes. */
      default Config withOperandFor(Class<? extends Project> projectClass,
          Class<MultiJoin> multiJoinClass) {
        return withOperandSupplier(b0 ->
            b0.operand(projectClass).oneInput(b1 ->
                b1.operand(multiJoinClass).anyInputs()))
            .as(Config.class);
      }
    }
  }
  