    001/*
    002 * Copyright (c) 2007-2017 Xplenty, 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.ElementExpression;
    025import cascading.flow.planner.iso.expression.ExpressionGraph;
    026import cascading.flow.planner.iso.expression.FlowElementExpression;
    027import cascading.flow.planner.iso.expression.TypeExpression;
    028import cascading.flow.planner.rule.RuleExpression;
    029import cascading.flow.planner.rule.expressiongraph.SyncPipeExpressionGraph;
    030import cascading.pipe.Group;
    031import cascading.pipe.HashJoin;
    032import cascading.pipe.Pipe;
    033import cascading.tap.Tap;
    034
    035import static cascading.flow.planner.iso.expression.OrElementExpression.or;
    036
    037/**
    038 *
    039 */
    040public class BalanceGroupSplitJoinExpression extends RuleExpression
    041  {
    042  public static final FlowElementExpression SHARED_GROUP = new FlowElementExpression( Group.class );
    043  public static final ElementExpression SHARED_JOIN = or( new FlowElementExpression( HashJoin.class ), new FlowElementExpression( Group.class ), new FlowElementExpression( Tap.class ) );
    044
    045  public BalanceGroupSplitJoinExpression()
    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        .arcs( SHARED_GROUP, SHARED_JOIN )
    053        .arcs( SHARED_GROUP, SHARED_JOIN ),
    054
    055      // sub-graph to match has out degree captured above
    056      new ExpressionGraph()
    057        .arcs(
    058          new FlowElementExpression( ElementCapture.Primary, Pipe.class, TypeExpression.Topo.SplitOnly )
    059        )
    060    );
    061    }
    062  }