001/* 002 * Copyright (c) 2016 Chris K Wensel <chris@wensel.net>. 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.flow.planner.rule.expression; 022 023import cascading.flow.planner.iso.expression.ElementCapture; 024import cascading.flow.planner.iso.expression.ElementExpression; 025import cascading.flow.planner.iso.expression.ExpressionGraph; 026import cascading.flow.planner.iso.expression.FlowElementExpression; 027import cascading.flow.planner.rule.RuleExpression; 028import cascading.flow.planner.rule.expressiongraph.ConsecutiveNoOpPipesExpressionGraph; 029import cascading.pipe.Pipe; 030import cascading.tap.Tap; 031 032import static cascading.flow.planner.iso.expression.OrElementExpression.or; 033 034/** 035 * This rule prevents a multi-graph from being formed when all no-op Pipe instances are removed from the assembly. 036 * <p> 037 * Adding support for multi-graphs in the FlowElementGraph is the better long term solution. 038 */ 039public class NoOpPipeMultiGraphExpression extends RuleExpression 040 { 041 public static final ElementExpression SPLIT = or( 042 new FlowElementExpression( Pipe.class ), new FlowElementExpression( Tap.class ) 043 ); 044 045 public static final ElementExpression JOIN = or( 046 new FlowElementExpression( Pipe.class ), new FlowElementExpression( Tap.class ) 047 ); 048 049 public NoOpPipeMultiGraphExpression() 050 { 051 super( 052 new ConsecutiveNoOpPipesExpressionGraph(), 053 new ExpressionGraph() 054 .arcs( 055 SPLIT, 056 new FlowElementExpression( ElementCapture.Primary, true, Pipe.class ), 057 JOIN 058 ) 059 .arcs( 060 SPLIT, 061 new FlowElementExpression( ElementCapture.Secondary, true, Pipe.class ), 062 JOIN 063 ) 064 ); 065 } 066 }