001/*
002 * Copyright (c) 2007-2015 Concurrent, 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  }