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 }