In the PostgreSQL, If you want to drop a function, you also have to mention the type of the parameters.

In this post, I am providing a script which populates DROP FUNCTION script with all the type of parameters.

For example:

One function definition is:

CREATE FUNCTION fn_test (id integer, name character varying);

You cannot drop this function using just DROP FUNCTION like:

DROP FUNCTION fn_test();

You have to also specify the type of the parameters like:

DROP FUNCTION fn_test(integer, character varying);

If we are going to drop multiple functions, we need a script for dropping all functions by specifying their relevant type of parameters.

Below is a script to solve this problem and using it you can get a full DROP FUNCTION script with the type of input parameters. You can select the require drop function script and execute it.

SELECT FORMAT('DROP FUNCTION %s(%s);'
             ,p.oid::regproc
             ,pg_get_function_identity_arguments(p.oid))
FROM pg_proc AS p 
INNER JOIN pg_namespace AS n 
	ON p.pronamespace = n.oid 
WHERE n.nspname NOT IN ('pg_catalog', 'information_schema');