CREATE FUNCTION

Introduced or updated: v1.2.339

Creates an external function that calls a remote handler over Flight (typically Python or other services).

Supported Languages

• Determined by the remote server (commonly Python, but any language can be used as long as it implements the Flight endpoint)

Syntax

CREATE [ OR REPLACE ] FUNCTION [ IF NOT EXISTS ] <function_name> 
    AS ( <input_param_types> ) RETURNS <return_type> LANGUAGE <language_name> 
    HANDLER = '<handler_name>' ADDRESS = '<udf_server_address>' 
    [DESC='<description>']

Parameter	Description
<function_name>	The name of the function.
<lambda_expression>	The lambda expression or code snippet defining the function's behavior.
DESC='<description>'	Description of the UDF.
<<input_param_names>	A list of input parameter names. Separated by comma.
<<input_param_types>	A list of input parameter types. Separated by comma.
<return_type>	The return type of the function.
LANGUAGE	Specifies the language used to write the function. Available values: python.
HANDLER = '<handler_name>'	Specifies the name of the function's handler.
ADDRESS = '<udf_server_address>'	Specifies the address of the UDF server.

Examples

This example walks through a complete end-to-end setup for an external function that calculates the greatest common divisor (GCD) of two integers.

Step 1: Set Up the Python UDF Server

Install the databend-udf package:

pip install databend-udf

Create a file udf_server.py with the following content:

from databend_udf import udf, UDFServer

@udf(
    input_types=["INT", "INT"],
    result_type="INT",
    skip_null=True,
)
def gcd(x: int, y: int) -> int:
    while y != 0:
        (x, y) = (y, x % y)
    return x

if __name__ == '__main__':
    server = UDFServer("0.0.0.0:8815")
    server.add_function(gcd)
    server.serve()

Start the server:

python udf_server.py

Step 2: Register the Function in Databend

CREATE FUNCTION gcd AS (INT, INT)
    RETURNS INT
    LANGUAGE python
    HANDLER = 'gcd'
    ADDRESS = 'http://localhost:8815';

Step 3: Call the Function

SELECT gcd(48, 18);
-- Returns: 6

SELECT gcd(100, 75);
-- Returns: 25