001/*
002 * Copyright (c) 2007-2016 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.flow.hadoop.planner.rule.expression;
022
023import cascading.flow.planner.iso.expression.ElementCapture;
024import cascading.flow.planner.iso.expression.ExpressionGraph;
025import cascading.flow.planner.iso.expression.FlowElementExpression;
026import cascading.flow.planner.iso.expression.NonSafeOperationExpression;
027import cascading.flow.planner.iso.expression.TypeExpression;
028import cascading.flow.planner.rule.RuleExpression;
029import cascading.flow.planner.rule.expressiongraph.NonSafeAndSplitAndSyncPipeExpressionGraph;
030import cascading.pipe.Pipe;
031import cascading.tap.Tap;
032
033/**
034 * Captures a split against a non-safe Operation to prevent the operation from running
035 * in parallel mappers.
036 * <p/>
037 * THis variant allows a non-safe operation to be followed by any Pipe. this assumes other rules
038 * enforce splitting to only be on Each or Pipe types.
039 */
040public class BalanceNonSafePipeSplitExpression extends RuleExpression
041  {
042  public BalanceNonSafePipeSplitExpression()
043    {
044    super(
045      new NonSafeAndSplitAndSyncPipeExpressionGraph(),
046
047      new ExpressionGraph()
048        .arcs(
049          new FlowElementExpression( Tap.class ),
050          new NonSafeOperationExpression(),
051          new FlowElementExpression( Pipe.class, TypeExpression.Topo.SplitOnly )
052        ),
053
054      new ExpressionGraph()
055        .arcs(
056          new FlowElementExpression( ElementCapture.Primary, Pipe.class, TypeExpression.Topo.Tail )
057        )
058    );
059    }
060  }