CREATE FUNCTION

CREATE FUNCTION creates a new user-defined function (UDF) in an existing database.

See more in our Python UDF (user-defined functions) guide.

Permissions

The role must have the CREATE FUNCTION permission at the database level.

Syntax

create_function_statement ::=
    CREATE [ OR REPLACE ] FUNCTION function_name (argument_list)
    RETURNS return_type
    AS $$
    { function_body }
    $$ LANGUAGE python
    ;

function_name ::= identifier

argument_list :: = { value_name type_name [, ...] }

value_name ::= identifier

return_type ::= type_name

function_body ::= Valid Python code

Parameters

Parameter	Description
`OR REPLACE`	Create a new function, and overwrite any existing function by the same name. Does not return an error if the function already exists. `CREATE OR REPLACE` does not check the function contents or structure, only the function name.
`function_name`	The name of the function to create, which must be unique inside the database.
`argument_list`	A comma separated list of column definitions. A column definition includes a name identifier and a datatype.
`return_type`	The SQL datatype of the return value, such as `INT`, `TEXT`, etc.
`function_body`	Python code, dollar-quoted (`$$`).

Examples

Calculate distance between two points

CREATE OR REPLACE FUNCTION my_distance (x1 float, y1 float, x2 float, y2 float)
  RETURNS FLOAT
  AS $$
import  math
if  y1  <  x1:
    return  0.0
else:
    return  math.sqrt((y2  -  y1)  **  2  +  (x2  -  x1)  **  2)
$$ LANGUAGE PYTHON;

-- Usage:
SELECT  city, my_location, my_distance(x1,y1,x2,y2)  from  cities;

Calling files from other locations

-- Our script my_code.py is in ~/my_python_stuff

CREATE FUNCTION write_log()
  RETURNS INT
  AS $$
import sys
sys.path.append("/home/user/my_python_stuff")

import my_code as f

f.main()

return 1

$$ LANGUAGE PYTHON;

-- Usage:
SELECT write_log();