001/*
002 * Copyright (c) 2007-2022 The Cascading Authors. All Rights Reserved.
003 *
004 * Project and contact information: https://cascading.wensel.net/
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.ScopeExpression;
027import cascading.flow.planner.iso.expression.TypeExpression.Topo;
028import cascading.flow.planner.rule.RuleExpression;
029import cascading.flow.planner.rule.expressiongraph.SyncPipeExpressionGraph;
030import cascading.pipe.Checkpoint;
031import cascading.pipe.Group;
032import cascading.pipe.HashJoin;
033import cascading.pipe.Pipe;
034import cascading.tap.Tap;
035
036import static cascading.flow.planner.iso.expression.OrElementExpression.or;
037
038/**
039 *
040 */
041public class BalanceGroupSplitExpression extends RuleExpression
042  {
043  public static final FlowElementExpression SHARED_GROUP = new FlowElementExpression( Group.class, Topo.Split );
044
045  public BalanceGroupSplitExpression()
046    {
047    super(
048      new SyncPipeExpressionGraph(),
049
050      // in order to capture out degree in sub-graph, we need to capture at least two successors
051      new ExpressionGraph()
052        .arc(
053          SHARED_GROUP,
054          ScopeExpression.ANY,
055          or( new FlowElementExpression( HashJoin.class ), new FlowElementExpression( Group.class ), new FlowElementExpression( Tap.class ), new FlowElementExpression( Checkpoint.class ) )
056        )
057
058        .arc(
059          SHARED_GROUP,
060          ScopeExpression.ANY,
061          or( new FlowElementExpression( HashJoin.class ), new FlowElementExpression( Group.class ), new FlowElementExpression( Tap.class ), new FlowElementExpression( Checkpoint.class ) )
062        ),
063
064      // sub-graph to match has out degree captured above
065      new ExpressionGraph()
066        .arcs(
067          new FlowElementExpression( ElementCapture.Primary, Pipe.class, Topo.SplitOnly )
068        )
069    );
070    }
071  }