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.convert;
  
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelOptCost;
  import org.apache.calcite.plan.RelOptPlanner;
  import org.apache.calcite.plan.RelTraitDef;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.SingleRel;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Abstract implementation of {@link Converter}.
   */
  public abstract class ConverterImpl extends SingleRel
      implements Converter {
    //~ Instance fields --------------------------------------------------------
  
    protected final RelTraitSet inTraits;
    protected final @Nullable RelTraitDef traitDef;
  
    //~ Constructors -----------------------------------------------------------
  
    /**
     * Creates a ConverterImpl.
     *
     * @param cluster  planner's cluster
     * @param traitDef the RelTraitDef this converter converts
     * @param traits   the output traits of this converter
     * @param child    child rel (provides input traits)
     */
    protected ConverterImpl(
        RelOptCluster cluster,
        @Nullable RelTraitDef traitDef,
        RelTraitSet traits,
        RelNode child) {
      super(cluster, traits, child);
      this.inTraits = child.getTraitSet();
      this.traitDef = traitDef;
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public @Nullable RelOptCost computeSelfCost(RelOptPlanner planner,
        RelMetadataQuery mq) {
      double dRows = mq.getRowCount(getInput());
      double dCpu = dRows;
      double dIo = 0;
      return planner.getCostFactory().makeCost(dRows, dCpu, dIo);
    }
  
    @Deprecated // to be removed before 2.0
    protected Error cannotImplement() {
      return new AssertionError(getClass() + " cannot convert from "
          + inTraits + " traits");
    }
  
    @Override public RelTraitSet getInputTraits() {
      return inTraits;
    }
  
    @Override public @Nullable RelTraitDef getTraitDef() {
      return traitDef;
    }
  
  }
  