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.mutable;
  
  import org.apache.calcite.rel.type.RelDataType;
  
  import com.google.common.collect.ImmutableList;
  
  import java.util.List;
  
  /** Mutable equivalent of {@link org.apache.calcite.rel.SingleRel}. */
  abstract class MutableSingleRel extends MutableRel {
    protected MutableRel input;
  
    @SuppressWarnings("initialization.invalid.field.write.initialized")
    protected MutableSingleRel(MutableRelType type,
        RelDataType rowType, MutableRel input) {
      super(input.cluster, rowType, type);
      this.input = input;
      input.parent = this;
      input.ordinalInParent = 0;
    }
  
    @Override public void setInput(int ordinalInParent, MutableRel input) {
      if (ordinalInParent > 0) {
        throw new IllegalArgumentException();
      }
      this.input = input;
      if (input != null) {
        input.parent = this;
        input.ordinalInParent = 0;
      }
    }
  
    @Override public List<MutableRel> getInputs() {
      return ImmutableList.of(input);
    }
  
    @Override public void childrenAccept(MutableRelVisitor visitor) {
      visitor.visit(input);
    }
  
    public MutableRel getInput() {
      return input;
    }
  }
  