/**
* 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.common.expression.visitors;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import org.apache.drill.common.expression.BooleanOperator;
import org.apache.drill.common.expression.CastExpression;
import org.apache.drill.common.expression.ConvertExpression;
import org.apache.drill.common.expression.FunctionCall;
import org.apache.drill.common.expression.FunctionHolderExpression;
import org.apache.drill.common.expression.IfExpression;
import org.apache.drill.common.expression.IfExpression.IfCondition;
import org.apache.drill.common.expression.LogicalExpression;
import com.google.common.collect.Lists;
public class ConditionalExprOptimizer extends AbstractExprVisitor<LogicalExpression, Void, RuntimeException> {
public static ConditionalExprOptimizer INSTANCE = new ConditionalExprOptimizer();
@Override
public LogicalExpression visitBooleanOperator(BooleanOperator op, Void value) throws RuntimeException {
List<LogicalExpression> newArgs = Lists.newArrayList();
newArgs.addAll(op.args);
Collections.sort(newArgs, costComparator);
return new BooleanOperator(op.getName(), newArgs, op.getPosition());
}
@Override
public LogicalExpression visitFunctionHolderExpression(FunctionHolderExpression holder, Void value) throws RuntimeException {
List<LogicalExpression> args = Lists.newArrayList();
for (int i = 0; i < holder.args.size(); ++i) {
LogicalExpression newExpr = holder.args.get(i).accept(this, value);
assert newExpr != null;
args.add(newExpr);
}
//replace with a new function call, since its argument could be changed.
return holder.copy(args);
}
@Override
public LogicalExpression visitUnknown(LogicalExpression e, Void value) throws RuntimeException {
return e;
}
@Override
public LogicalExpression visitIfExpression(IfExpression ifExpr, Void value) throws RuntimeException{
LogicalExpression newElseExpr = ifExpr.elseExpression.accept(this, value);
IfCondition conditions = ifExpr.ifCondition;
LogicalExpression newCondition = conditions.condition.accept(this, value);
LogicalExpression newExpr = conditions.expression.accept(this, value);
conditions = new IfExpression.IfCondition(newCondition, newExpr);
return IfExpression.newBuilder().setElse(newElseExpr).setIfCondition(conditions).build();
}
@Override
public LogicalExpression visitFunctionCall(FunctionCall call, Void value) throws RuntimeException {
throw new UnsupportedOperationException("FunctionCall is not expected here. "
+ "It should have been converted to FunctionHolderExpression in materialization");
}
@Override
public LogicalExpression visitCastExpression(CastExpression cast, Void value) throws RuntimeException {
throw new UnsupportedOperationException("CastExpression is not expected here. "
+ "It should have been converted to FunctionHolderExpression in materialization");
}
@Override
public LogicalExpression visitConvertExpression(ConvertExpression cast, Void value) throws RuntimeException {
throw new UnsupportedOperationException("ConvertExpression is not expected here. "
+ "It should have been converted to FunctionHolderExpression in materialization");
}
private static Comparator<LogicalExpression> costComparator = new Comparator<LogicalExpression> () {
public int compare(LogicalExpression e1, LogicalExpression e2) {
return e1.getCumulativeCost() <= e2.getCumulativeCost() ? -1 : 1;
}
};
}