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

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Java | 51 lines | 21 code | 6 blank | 24 comment | 4 complexity | 35a6c5cc02c60544353d6a2325ee987a MD5 | raw file
 1/**
 2 * Licensed to the Apache Software Foundation (ASF) under one
 3 * or more contributor license agreements.  See the NOTICE file
 4 * distributed with this work for additional information
 5 * regarding copyright ownership.  The ASF licenses this file
 6 * to you under the Apache License, Version 2.0 (the
 7 * "License"); you may not use this file except in compliance
 8 * with the License.  You may obtain a copy of the License at
 9 *
10 *     http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18
19package org.apache.hadoop.hive.ql.udf;
20
21import org.apache.hadoop.hive.ql.exec.Description;
22import org.apache.hadoop.hive.ql.exec.UDF;
23import org.apache.hadoop.hive.serde2.io.DoubleWritable;
24
25/**
26 * UDFLn.
27 *
28 */
29@Description(name = "ln",
30    value = "_FUNC_(x) - Returns the natural logarithm of x",
31    extended = "Example:\n"
32    + "  > SELECT _FUNC_(1) FROM src LIMIT 1;\n" + "  0")
33public class UDFLn extends UDF {
34  private DoubleWritable result = new DoubleWritable();
35
36  public UDFLn() {
37  }
38
39  /**
40   * Returns the natural logarithm of "a".
41   */
42  public DoubleWritable evaluate(DoubleWritable a) {
43    if (a == null || a.get() <= 0.0) {
44      return null;
45    } else {
46      result.set(Math.log(a.get()));
47      return result;
48    }
49  }
50
51}