Use the DROP FUNCTION command to remove an existing user-defined function (UDF).

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Syntax

DROP FUNCTION [ IF EXISTS ] function_name [ ( argument_type [, ...] ) ] ;
Parameter or clauseDescription
function_nameName of the UDF you want to drop.
( argument_type [ , … ] )Optional: Argument types of the function.Specify the argument types when the name of the function you want to drop isn’t unique within the schema.
IF EXISTSDo not return an error if the specified function does not exist. A notice is issued in this case.

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Usage

A function can be dropped using one of the following methods:
  • Full function signature:
DROP FUNCTION function_name ( argument_type [, ...] );
  • Function name only, if it’s unique in its schema:
DROP FUNCTION function_name;
You can run SHOW FUNCTIONS; to list all existing UDFs to see if a function name is unique.
DROP FUNCTION function_name(); drops a function with zero arguments.DROP FUNCTION function_name; drops a function with any number of arguments, including zero, as long as the name is unique.

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Examples

First, let’s create some functions. 
CREATE FUNCTION f1() RETURNS real LANGUAGE python AS func1 USING LINK 'http://localhost:8815';
CREATE FUNCTION f1(int) RETURNS int LANGUAGE python AS func2 USING LINK 'http://localhost:8815';
CREATE FUNCTION f1(int,int) RETURNS int LANGUAGE python AS func3 USING LINK 'http://localhost:8815';
CREATE FUNCTION f2(int,int) RETURNS int LANGUAGE python AS func4 USING LINK 'http://localhost:8815';
You can drop a unique function by name: 
DROP FUNCTION f2;
You cannot drop a function by name when its name is not unique: 
DROP FUNCTION f1;

ERROR:  QueryError: Catalog error: function name "f1" is not unique
HINT: Specify the argument list to select the function unambiguously.
You can drop a function by full signature: 
DROP FUNCTION f1();
DROP FUNCTION f1(int);
Now, f1(int,int) is the only function named f1, you can drop it by name or full signature: 
DROP FUNCTION f1;
-- Or DROP FUNCTION f1(int,int);

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See also

User-defined functions

A step-by-step guide for using UDFs in RisingWave: installing the RisingWave UDF API, defining functions in a Python file, starting the UDF server, and declaring UDFs in RisingWave.

SHOW FUNCTIONS

Show all existing UDFs