001/* 002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved. 003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved. 004 * 005 * Project and contact information: http://www.cascading.org/ 006 * 007 * This file is part of the Cascading project. 008 * 009 * Licensed under the Apache License, Version 2.0 (the "License"); 010 * you may not use this file except in compliance with the License. 011 * You may obtain a copy of the License at 012 * 013 * http://www.apache.org/licenses/LICENSE-2.0 014 * 015 * Unless required by applicable law or agreed to in writing, software 016 * distributed under the License is distributed on an "AS IS" BASIS, 017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 018 * See the License for the specific language governing permissions and 019 * limitations under the License. 020 */ 021 022package cascading.pipe; 023 024import cascading.flow.planner.Scope; 025import cascading.tuple.Fields; 026 027/** 028 * The Boundary class is only used internally by the planner to mark the boundaries between partitions within 029 * the element graph. 030 * <p> 031 * In MapReduce, Taps are used. But in DAG models, Boundary would specify where a system dependent interface should 032 * be used. 033 */ 034public class Boundary extends Pipe 035 { 036 /** 037 * Intentionally does not provide a chaining constructor, as Boundary should not be inserted into an assembly 038 * by a user. 039 */ 040 public Boundary() 041 { 042 } 043 044 @Override 045 public String getName() 046 { 047 return Pipe.id( this ); 048 } 049 050 @Override 051 public Fields resolveIncomingOperationPassThroughFields( Scope incomingScope ) 052 { 053 return incomingScope.getIncomingFunctionPassThroughFields(); 054 } 055 }