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.logical;
  
  import org.apache.calcite.plan.Convention;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelDistribution;
  import org.apache.calcite.rel.RelDistributionTraitDef;
  import org.apache.calcite.rel.RelInput;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.RelShuttle;
  import org.apache.calcite.rel.core.Exchange;
  
  /**
   * Sub-class of {@link Exchange} not
   * targeted at any particular engine or calling convention.
   */
  public final class LogicalExchange extends Exchange {
    private LogicalExchange(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode input, RelDistribution distribution) {
      super(cluster, traitSet, input, distribution);
      assert traitSet.containsIfApplicable(Convention.NONE);
    }
  
    /**
     * Creates a LogicalExchange by parsing serialized output.
     */
    public LogicalExchange(RelInput input) {
      super(input);
    }
  
    /**
     * Creates a LogicalExchange.
     *
     * @param input     Input relational expression
     * @param distribution Distribution specification
     */
    public static LogicalExchange create(RelNode input,
        RelDistribution distribution) {
      RelOptCluster cluster = input.getCluster();
      distribution = RelDistributionTraitDef.INSTANCE.canonize(distribution);
      RelTraitSet traitSet =
          input.getTraitSet().replace(Convention.NONE).replace(distribution);
      return new LogicalExchange(cluster, traitSet, input, distribution);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public Exchange copy(RelTraitSet traitSet, RelNode newInput,
        RelDistribution newDistribution) {
      return new LogicalExchange(getCluster(), traitSet, newInput,
          newDistribution);
    }
  
    @Override public RelNode accept(RelShuttle shuttle) {
      return shuttle.visit(this);
    }
  }
  