/tags/release-0.0.0-rc0/hive/external/ql/src/java/org/apache/hadoop/hive/ql/udf/UDFSqrt.java

/**
 * 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;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.hive.serde2.io.DoubleWritable;

/**
 * Implementation of the SQRT UDF found in many databases.
 */
@Description(name = "sqrt",
    value = "_FUNC_(x) - returns the square root of x",
    extended = "Example:\n "
    + "  > SELECT _FUNC_(4) FROM src LIMIT 1;\n" + "  2")
public class UDFSqrt extends UDF {
  private DoubleWritable result = new DoubleWritable();

  public UDFSqrt() {
  }

  /**
   * Return NULL for NULL or negative inputs; otherwise, return the square root.
   */
  public DoubleWritable evaluate(DoubleWritable i) {
    if (i == null) {
      return null;
    } else if (i.get() < 0) {
      return null;
    } else {
      result.set(Math.sqrt(i.get()));
      return result;
    }
  }

}