| ############## |
| Hive Functions |
| ############## |
| |
| Tajo provides a feature to use Hive functions directly without re-compilation or additional code. |
| |
| ************* |
| Configuration |
| ************* |
| |
| Only thing to do is registering path to a directory for jar files containing your hive functions. |
| You can do this by set ``tajo.function.hive.jar-dir`` in ``tajo-site.xml`` like the following. |
| |
| .. code-block:: xml |
| |
| <property> |
| <name>tajo.function.hive.jar-dir</name> |
| <value>/path/to/hive/function/jar</value> |
| </property> |
| |
| .. note:: |
| The path should be one in local filesystem. HDFS directory is not supported because of JAVA URI compatability problem. |
| |
| .. warning:: |
| |
| The path must point to a directory, not a file. And multiple directory entries are not allowed. |
| However, it is possible to load multiple jar files. |
| |
| *************** |
| Using in detail |
| *************** |
| |
| ============= |
| Function Name |
| ============= |
| |
| Tajo reads hive functions override ``org.apache.hadoop.hive.ql.exec.UDF`` class. Function name is used as specified in |
| ``@Description`` annotation. If it doesn't exist, Tajo uses full qualified class name as function name. For example, |
| it can be like this : ``select com_example_hive_udf_myupper('abcd')``, so it is recommended to use Description annotation. |
| |
| Additionally if some function signature duplicate occurs, it may throw ``AmbiguousFunctionException``. |
| |
| ============================ |
| Parameter type / Return type |
| ============================ |
| |
| Hive uses *Writable* type of Hadoop in functions, but Tajo uses its internal *Datum* type. |
| So only some Writable types are supported currently by internal converting. |
| They are listed below. |
| |
| ==================== ========= |
| Writable Tajo Type |
| ==================== ========= |
| ByteWritable INT1 |
| ShortWritable INT2 |
| IntWritable INT4 |
| LongWritable INT8 |
| FloatWritable FLOAT4 |
| DoubleWritable FLOAT8 |
| Text TEXT |
| BytesWritable VARBINARY |
| DateWritable(*) DATE |
| TimestampWritable(*) TIMESTAMP |
| HiveCharWritable(*) CHAR |
| ==================== ========= |
| |
| .. note:: |
| |
| (*) They are in org.apache.hadoop.hive.serde2.io package, others are in org.apache.hadoop.io package. |
| |
| ========== |
| Limitation |
| ========== |
| |
| 1. Currently, Hive UDAF is not supported. Old UDAF interface is deprecated in Hive, |
| and new GenericUDAF interface cannot be applied because of function design difference between Tajo and Hive. |
| For same reason, new GenericUDF functions are not supported in Tajo. |
| |
| 2. Because HDFS directory is not supported, Hive UDF jar files should be copied to each worker directory and each path |
| should be specified in tajo-site.xml. |
