/*
* Copyright (c) 2007-2014 Concurrent, Inc. All Rights Reserved.
*
* Project and contact information: http://www.cascading.org/
*
* This file is part of the Cascading project.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cascading.flow.hadoop.planner.rule.expression;
import cascading.flow.planner.iso.expression.ElementCapture;
import cascading.flow.planner.iso.expression.ExpressionGraph;
import cascading.flow.planner.iso.expression.FlowElementExpression;
import cascading.flow.planner.iso.expression.TypeExpression;
import cascading.flow.planner.rule.RuleExpression;
import cascading.flow.planner.rule.expressiongraph.SyncPipeExpressionGraph;
import cascading.pipe.Group;
import cascading.pipe.HashJoin;
import cascading.pipe.Pipe;
import cascading.tap.Tap;
import static cascading.flow.planner.iso.expression.OrElementExpression.or;
/**
*
*/
public class BalanceGroupSplitExpression extends RuleExpression
{
public static final FlowElementExpression SHARED_GROUP = new FlowElementExpression( Group.class );
public BalanceGroupSplitExpression()
{
super(
new SyncPipeExpressionGraph(),
// in order to capture out degree in sub-graph, we need to capture at least two successors
new ExpressionGraph()
.arcs( SHARED_GROUP, or( new FlowElementExpression( HashJoin.class ), new FlowElementExpression( Group.class ), new FlowElementExpression( Tap.class ) ) )
.arcs( SHARED_GROUP, or( new FlowElementExpression( HashJoin.class ), new FlowElementExpression( Group.class ), new FlowElementExpression( Tap.class ) ) ),
// sub-graph to match has out degree captured above
new ExpressionGraph()
.arcs(
new FlowElementExpression( ElementCapture.Primary, Pipe.class, TypeExpression.Topo.SplitOnly )
)
);
}
}