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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.drill.exec.planner.physical.visitor;
import java.util.List;
import java.util.Set;
import org.apache.drill.exec.planner.physical.Prel;
import org.eigenbase.rel.RelNode;
import com.google.common.collect.Sets;
import com.google.common.collect.Lists;
public class RelUniqifier extends BasePrelVisitor<Prel, Set<Prel>, RuntimeException>{
static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(RelUniqifier.class);
private static final RelUniqifier INSTANCE = new RelUniqifier();
public static Prel uniqifyGraph(Prel p){
Set<Prel> data = Sets.newIdentityHashSet();
return p.accept(INSTANCE, data);
}
@Override
public Prel visitPrel(Prel prel, Set<Prel> data) throws RuntimeException {
List<RelNode> children = Lists.newArrayList();
boolean childrenChanged = false;
for(Prel child : prel){
Prel newChild = visitPrel(child, data);
if(newChild != child) childrenChanged = true;
children.add(newChild);
}
if(data.contains(prel) || childrenChanged){
return (Prel) prel.copy(prel.getTraitSet(), children);
}else{
return prel;
}
}
}
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