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.metadata;
  
  import org.apache.calcite.plan.RelOptCost;
  import org.apache.calcite.plan.volcano.RelSubset;
  import org.apache.calcite.plan.volcano.VolcanoPlanner;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.metadata.BuiltInMetadata.LowerBoundCost;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Default implementations of the
   * {@link BuiltInMetadata.LowerBoundCost}
   * metadata provider for the standard algebra.
   */
  public class RelMdLowerBoundCost implements MetadataHandler<LowerBoundCost> {
  
    public static final RelMetadataProvider SOURCE =
        ReflectiveRelMetadataProvider.reflectiveSource(
            new RelMdLowerBoundCost(), LowerBoundCost.Handler.class);
  
    //~ Constructors -----------------------------------------------------------
  
    protected RelMdLowerBoundCost() {}
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public MetadataDef<LowerBoundCost> getDef() {
      return BuiltInMetadata.LowerBoundCost.DEF;
    }
  
    public @Nullable RelOptCost getLowerBoundCost(RelSubset subset,
        RelMetadataQuery mq, VolcanoPlanner planner) {
  
      if (planner.isLogical(subset)) {
        // currently only support physical, will improve in the future
        return null;
      }
  
      return subset.getWinnerCost();
    }
  
    public @Nullable RelOptCost getLowerBoundCost(RelNode node,
        RelMetadataQuery mq, VolcanoPlanner planner) {
      if (planner.isLogical(node)) {
        // currently only support physical, will improve in the future
        return null;
      }
  
      RelOptCost selfCost = mq.getNonCumulativeCost(node);
      if (selfCost != null && selfCost.isInfinite()) {
        selfCost = null;
      }
      for (RelNode input : node.getInputs()) {
        RelOptCost lb = mq.getLowerBoundCost(input, planner);
        if (lb != null) {
          selfCost = selfCost == null ? lb : selfCost.plus(lb);
        }
      }
      return selfCost;
    }
  }
  