/*
* 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 com.facebook.presto.sql.planner;
import com.facebook.presto.sql.tree.DefaultExpressionTraversalVisitor;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.sql.tree.FunctionCall;
import com.facebook.presto.sql.tree.QualifiedName;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Determines whether a given Expression is deterministic
*/
public final class DeterminismEvaluator
{
private DeterminismEvaluator() {}
public static boolean isDeterministic(Expression expression)
{
Preconditions.checkNotNull(expression, "expression is null");
AtomicBoolean deterministic = new AtomicBoolean(true);
new Visitor().process(expression, deterministic);
return deterministic.get();
}
public static Predicate<Expression> deterministic()
{
return new Predicate<Expression>()
{
@Override
public boolean apply(Expression expression)
{
return isDeterministic(expression);
}
};
}
private static class Visitor
extends DefaultExpressionTraversalVisitor<Void, AtomicBoolean>
{
@Override
protected Void visitFunctionCall(FunctionCall node, AtomicBoolean deterministic)
{
// TODO: total hack to figure out if a function is deterministic. martint should fix this when he refactors the planning code
if (node.getName().equals(new QualifiedName("rand")) || node.getName().equals(new QualifiedName("random"))) {
deterministic.set(false);
}
return super.visitFunctionCall(node, deterministic);
}
}
}