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

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Java | 64 lines | 33 code | 9 blank | 22 comment | 1 complexity | ef4ce7d7c309c63e4d9b13bb3c112286 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.generic;
20
21import org.apache.commons.lang.StringUtils;
22import org.apache.hadoop.hive.ql.exec.Description;
23import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
24import org.apache.hadoop.hive.ql.metadata.HiveException;
25import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
26import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils;
27import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
28import org.apache.hadoop.io.IntWritable;
29
30/**
31 * GenericUDF Class for computing hash values.
32 */
33@Description(name = "hash", value = "_FUNC_(a1, a2, ...) - Returns a hash value of the arguments")
34public class GenericUDFHash extends GenericUDF {
35  private ObjectInspector[] argumentOIs;
36
37  @Override
38  public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentTypeException {
39
40    argumentOIs = arguments;
41    return PrimitiveObjectInspectorFactory.writableIntObjectInspector;
42  }
43
44  private IntWritable result = new IntWritable();
45
46  @Override
47  public Object evaluate(DeferredObject[] arguments) throws HiveException {
48    // See
49    // http://java.sun.com/j2se/1.5.0/docs/api/java/util/List.html#hashCode()
50    int r = 0;
51    for (int i = 0; i < arguments.length; i++) {
52      r = r * 31
53          + ObjectInspectorUtils.hashCode(arguments[i].get(), argumentOIs[i]);
54    }
55    result.set(r);
56    return result;
57  }
58
59  @Override
60  public String getDisplayString(String[] children) {
61    return "hash(" + StringUtils.join(children, ',') + ")";
62  }
63
64}