    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  }