GenericUDFOPNull.java example

Explorer
hive-master
/**
 * 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.hadoop.hive.ql.udf.generic;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.exec.vector.VectorizedExpressions;
import org.apache.hadoop.hive.ql.exec.vector.expressions.IsNull;
import org.apache.hadoop.hive.ql.exec.vector.expressions.SelectColumnIsNull;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.io.BooleanWritable;

/**
 * GenericUDFOPNull.
 *
 */
@Description(name = "isnull", value = "_FUNC_ a - Returns true if a is NULL and false otherwise")
@VectorizedExpressions({IsNull.class, SelectColumnIsNull.class})
@NDV(maxNdv = 2)
public class GenericUDFOPNull extends GenericUDF {
  private final BooleanWritable result = new BooleanWritable();

  @Override
  public ObjectInspector initialize(ObjectInspector[] arguments)
      throws UDFArgumentException {
    if (arguments.length != 1) {
      throw new UDFArgumentLengthException(
          "The operator 'IS NULL' only accepts 1 argument.");
    }
    return PrimitiveObjectInspectorFactory.writableBooleanObjectInspector;
  }

  @Override
  public Object evaluate(DeferredObject[] arguments) throws HiveException {
    result.set(arguments[0].get() == null);
    return result;
  }

  @Override
  public String getDisplayString(String[] children) {
    assert (children.length == 1);
    return children[0] + " is null";
  }

  @Override
  public GenericUDF negative() {
    return new GenericUDFOPNotNull();
  }
}