| /* |
| * 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; |
| |
| import java.util.Collections; |
| import java.util.Iterator; |
| |
| import org.apache.drill.common.expression.visitors.ExprVisitor; |
| import org.apache.drill.common.types.TypeProtos.MajorType; |
| import org.apache.drill.common.types.TypeProtos.MinorType; |
| import org.apache.drill.common.types.Types; |
| |
| public class NullExpression implements LogicalExpression{ |
| static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(NullExpression.class); |
| |
| public static final NullExpression INSTANCE = new NullExpression(); |
| |
| final MajorType t = Types.optional(MinorType.NULL); |
| |
| @Override |
| public MajorType getMajorType() { |
| return t; |
| } |
| |
| @Override |
| public <T, V, E extends Exception> T accept(ExprVisitor<T, V, E> visitor, V value) throws E { |
| return visitor.visitNullExpression(this, value); |
| } |
| |
| @Override |
| public ExpressionPosition getPosition() { |
| return ExpressionPosition.UNKNOWN; |
| } |
| |
| @Override |
| public Iterator<LogicalExpression> iterator() { |
| return Collections.emptyIterator(); |
| } |
| |
| public int getSelfCost() { return 0; } |
| |
| public int getCumulativeCost() { return 0; } |
| |
| } |