    001/*
    002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
    003 *
    004 * Project and contact information: http://www.cascading.org/
    005 *
    006 * This file is part of the Cascading project.
    007 *
    008 * Licensed under the Apache License, Version 2.0 (the "License");
    009 * you may not use this file except in compliance with the License.
    010 * You may obtain a copy of the License at
    011 *
    012 *     http://www.apache.org/licenses/LICENSE-2.0
    013 *
    014 * Unless required by applicable law or agreed to in writing, software
    015 * distributed under the License is distributed on an "AS IS" BASIS,
    016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017 * See the License for the specific language governing permissions and
    018 * limitations under the License.
    019 */
    020
    021package cascading.pipe;
    022
    023import cascading.flow.planner.Scope;
    024import cascading.tuple.Fields;
    025
    026/**
    027 * The Boundary class is only used internally by the planner to mark the boundaries between partitions within
    028 * the element graph.
    029 * <p/>
    030 * In MapReduce, Taps are used. But in DAG models, Boundary would specify where a system dependent interface should
    031 * be used.
    032 */
    033public class Boundary extends Pipe
    034  {
    035  /**
    036   * Intentionally does not provide a chaining constructor, as Boundary should not be inserted into an assembly
    037   * by a user.
    038   */
    039  public Boundary()
    040    {
    041    }
    042
    043  @Override
    044  public String getName()
    045    {
    046    return Pipe.id( this );
    047    }
    048
    049  @Override
    050  public Fields resolveIncomingOperationPassThroughFields( Scope incomingScope )
    051    {
    052    return incomingScope.getIncomingFunctionPassThroughFields();
    053    }
    054  }