Example UDF (Non-CUDA) - Sum of Squares

The following is a complete example, using the Python API, of a non-CUDA UDF that takes a list of input tables and corresponding output tables (must be the same number) and, for each record of each input table, sums the squares of input table columns and saves the result to the corresponding output table column; i.e.:

in.a2 + in.b2 + ... + in.n2 -> out.a

This setup assumes the UDF is being developed on the Kinetica host (or head node host, if a multi-node Kinetica cluster); and that the Python database API is available at /opt/gpudb/api/python and the Python UDF API is available at /opt/gpudb/udf/api/python.

This example will contain the following Python scripts (click to download):

Note

All commands should be run as the gpudb user.

After copying these three scripts to a gpudb-accessible directory on the Kinetica head node, the example can be run as follows, optionally specifying the database host and a username & password to the Python scripts:

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$ /opt/gpudb/bin/gpudb_python udf_sos_py_init.py [--host <kinetica-host> [--username <kinetica-user> --password <kinetica-pass>]]
$ /opt/gpudb/bin/gpudb_python udf_sos_py_exec.py [--host <kinetica-host> [--username <kinetica-user> --password <kinetica-pass>]]

The results of the run can be checked via Kinetica Administration Application (GAdmin). There should exist two tables within the example_udf_python schema, udf_sos_in_table & udf_sos_out_table, each holding 10,000 records; the former containing pairs of numbers and the latter containing the sums of squares of those numbers. Each table will carry an id, which can be used to associate input values to output sums.

To verify the existence of the tables, in GAdmin, click Data > Tables. Both tables should appear in the example_udf_python schema, each with 10,000 records.

To verify the calculations, click Query > KiSQL. Enter the following query into the SQL Statement box:

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SELECT
   sos_in.id,
   STRING(x1) || '^2 + ' || STRING(x2) || '^2 = ' || STRING(y) AS "Equation"
FROM
   example_udf_python.udf_sos_in_table sos_in,
   example_udf_python.udf_sos_out_table sos_out
WHERE
   sos_in.id = sos_out.id
ORDER BY
   id;

The Query Result box should show each of the 10,000 calculations made.

Execution Detail

While the example UDF itself can run against multiple tables, the example run will use a single schema-qualified table, example_udf_python.udf_sos_in_table`, as input and a matching schema-qualified table, example_udf_python.udf_sos_out_table, for output.

The input table will contain two float columns and be populated with 10,000 pairs of randomly-generated numbers. The output table will contain one float column that will hold the sums calculated by the UDF. Both tables will also contain an int column that is the calculation identifier, allowing the input data to be matched up with the output data after the UDF has run.

Note

The UDF will assume the first column of the input table, as defined in the original table creation process, is the identifier field. All of the remaining columns after the first will be used in the sum-of-squares calculation.

The UDF will calculate the sum of the squares of each of the 10,000 pairs of numbers and insert into the output table the corresponding 10,000 sums.

udf_sos_py_init.py

This initialization script creates the schema, input & output tables, and populates the input data using the standard Kinetica Python API, all outside of the UDF execution framework.

Several aspects of the initialization process are noteworthy:

  • The external database connection, indicative of the use of the standard Kinetica Python API--the UDF will not have this, as it runs within the database:
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kinetica = gpudb.GPUdb(host=['http://' + args.host + ':9191'], username=args.username, password=args.password)
  • Schema, input, and output table creation:
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kinetica.create_schema(SCHEMA, options=OPTION_NO_CREATE_ERROR)
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columns = []
columns.append(gpudb.GPUdbRecordColumn("id", gpudb.GPUdbRecordColumn._ColumnType.INT, [gpudb.GPUdbColumnProperty.PRIMARY_KEY, gpudb.GPUdbColumnProperty.INT16]))
columns.append(gpudb.GPUdbRecordColumn("x1", gpudb.GPUdbRecordColumn._ColumnType.FLOAT))
columns.append(gpudb.GPUdbRecordColumn("x2", gpudb.GPUdbRecordColumn._ColumnType.FLOAT))
input_table = gpudb.GPUdbTable(columns, INPUT_TABLE, db = kinetica)
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columns = []
columns.append(gpudb.GPUdbRecordColumn("id", gpudb.GPUdbRecordColumn._ColumnType.INT, [gpudb.GPUdbColumnProperty.PRIMARY_KEY, gpudb.GPUdbColumnProperty.INT16]))
columns.append(gpudb.GPUdbRecordColumn("y", gpudb.GPUdbRecordColumn._ColumnType.FLOAT))
gpudb.GPUdbTable(columns, OUTPUT_TABLE, db = kinetica)

udf_sos_py_proc.py

This is the UDF itself. It uses the Kinetica Python UDF API to compute the sums of squares of input table columns and output those sums to an output table. It runs within the UDF execution framework, and as such, is not called directly--instead, it is registered and launched by udf_sos_py_exec.py.

Noteworthy in the UDF are the following:

  • The initial call to ProcData() to access the database:
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proc_data = ProcData()
  • The size of the output table must be specified before writing to it:
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out_table.size = in_table.size
  • The final call to complete() to mark the process as finished and ready for clean-up:
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proc_data.complete()

udf_sos_py_exec.py

The execution script uses the standard Kinetica Python API to register the UDF in the database and then execute it.

The registration step associates a name with the UDF execution code contained in udf_sos_py_proc.py, the command ( python ) and arguments (the name of the proc script) to use to run it, and that it will run in distributed mode.

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response = kinetica.create_proc(proc_name, 'distributed', files, 'python', [file_name], {})

The execution step invokes the UDF by name, passing in the input & output table names against which the UDF will execute.

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response = kinetica.execute_proc(proc_name, {}, {}, [INPUT_TABLE], {}, [OUTPUT_TABLE], {})