com.facebook.presto.sql.planner.DeterminismEvaluator.java Source code

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Here is the source code for com.facebook.presto.sql.planner.DeterminismEvaluator.java

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/*
 * 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 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();
    }

    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);
        }
    }
}