    001/*
    002 * Copyright (c) 2016 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.flow.hadoop.planner.rule.expression;
    023
    024import cascading.flow.planner.iso.expression.ElementCapture;
    025import cascading.flow.planner.iso.expression.ExpressionGraph;
    026import cascading.flow.planner.iso.expression.FlowElementExpression;
    027import cascading.flow.planner.iso.expression.ScopeExpression;
    028import cascading.flow.planner.iso.expression.TypeExpression.Topo;
    029import cascading.flow.planner.rule.RuleExpression;
    030import cascading.flow.planner.rule.expressiongraph.SyncPipeExpressionGraph;
    031import cascading.pipe.Checkpoint;
    032import cascading.pipe.Group;
    033import cascading.pipe.HashJoin;
    034import cascading.pipe.Pipe;
    035import cascading.tap.Tap;
    036
    037import static cascading.flow.planner.iso.expression.OrElementExpression.or;
    038
    039/**
    040 *
    041 */
    042public class BalanceGroupSplitExpression extends RuleExpression
    043  {
    044  public static final FlowElementExpression SHARED_GROUP = new FlowElementExpression( Group.class, Topo.Split );
    045
    046  public BalanceGroupSplitExpression()
    047    {
    048    super(
    049      new SyncPipeExpressionGraph(),
    050
    051      // in order to capture out degree in sub-graph, we need to capture at least two successors
    052      new ExpressionGraph()
    053        .arc(
    054          SHARED_GROUP,
    055          ScopeExpression.ANY,
    056          or( new FlowElementExpression( HashJoin.class ), new FlowElementExpression( Group.class ), new FlowElementExpression( Tap.class ), new FlowElementExpression( Checkpoint.class ) )
    057        )
    058
    059        .arc(
    060          SHARED_GROUP,
    061          ScopeExpression.ANY,
    062          or( new FlowElementExpression( HashJoin.class ), new FlowElementExpression( Group.class ), new FlowElementExpression( Tap.class ), new FlowElementExpression( Checkpoint.class ) )
    063        ),
    064
    065      // sub-graph to match has out degree captured above
    066      new ExpressionGraph()
    067        .arcs(
    068          new FlowElementExpression( ElementCapture.Primary, Pipe.class, Topo.SplitOnly )
    069        )
    070    );
    071    }
    072  }