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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.pig.backend.hadoop.executionengine.mapReduceLayer;
import java.util.List;
import java.util.LinkedList;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.plans.MROpPlanVisitor;
import org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.plans.MROperPlan;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhysicalPlan;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POFilter;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.ConstantExpression;
import org.apache.pig.impl.plan.PlanException;
import org.apache.pig.impl.plan.DependencyOrderWalker;
import org.apache.pig.impl.plan.VisitorException;
import org.apache.pig.impl.util.Pair;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhyPlanVisitor;
/**
* For historical reasons splits will always produce filters that pass
* everything through unchanged. This optimizer removes these. This
* optimizer is also a pre-req for the NoopStoreRemover.
*
* The condition we look for is POFilters with a constant boolean
* (true) expression as it's plan.
*/
class NoopFilterRemover extends MROpPlanVisitor {
private Log log = LogFactory.getLog(getClass());
NoopFilterRemover(MROperPlan plan) {
super(plan, new DependencyOrderWalker<MapReduceOper, MROperPlan>(plan));
}
@Override
public void visitMROp(MapReduceOper mr) throws VisitorException {
new PhysicalRemover(mr.mapPlan).visit();
new PhysicalRemover(mr.combinePlan).visit();
new PhysicalRemover(mr.reducePlan).visit();
}
private class PhysicalRemover extends PhyPlanVisitor {
private List< Pair<POFilter, PhysicalPlan> > removalQ;
PhysicalRemover(PhysicalPlan plan) {
super(plan, new DependencyOrderWalker<PhysicalOperator, PhysicalPlan>(plan));
removalQ = new LinkedList< Pair<POFilter, PhysicalPlan> >();
}
@Override
public void visit() throws VisitorException {
super.visit();
for (Pair<POFilter, PhysicalPlan> pair: removalQ) {
removeFilter(pair.first, pair.second);
}
removalQ.clear();
}
@Override
public void visitFilter(POFilter fl) throws VisitorException {
PhysicalPlan filterPlan = fl.getPlan();
if (filterPlan.size() == 1) {
PhysicalOperator op = filterPlan.getRoots().get(0);
if (op instanceof ConstantExpression) {
ConstantExpression exp = (ConstantExpression)op;
Object value = exp.getValue();
if (value instanceof Boolean) {
Boolean filterValue = (Boolean)value;
if (filterValue) {
removalQ.add(new Pair(fl, mCurrentWalker.getPlan()));
}
}
}
}
}
private void removeFilter(POFilter filter, PhysicalPlan plan) {
if (plan.size() > 1) {
try {
List<PhysicalOperator> fInputs = filter.getInputs();
List<PhysicalOperator> sucs = plan.getSuccessors(filter);
plan.removeAndReconnect(filter);
if(sucs!=null && sucs.size()!=0){
for (PhysicalOperator suc : sucs) {
suc.setInputs(fInputs);
}
}
} catch (PlanException pe) {
log.info("Couldn't remove a filter in optimizer: "+pe.getMessage());
}
}
}
}
}