DROP ROUTINE — remove a routine
DROP ROUTINE [ IF EXISTS ]name[ ( [ [argmode] [argname]argtype[, ...] ] ) ] [, ...] [ CASCADE | RESTRICT ]
DROP ROUTINE removes the definition of an existing routine, which can be an aggregate function, a normal function, or a procedure. See under DROP AGGREGATE, DROP FUNCTION, and DROP PROCEDURE for the description of the parameters, more examples, and further details.
To drop the routine foo for type integer:
DROP ROUTINE foo(integer);
This command will work independent of whether foo is an aggregate, function, or procedure.
This command conforms to the SQL standard, with these PostgreSQL extensions:
The standard only allows one routine to be dropped per command.
The IF EXISTS option
The ability to specify argument modes and names
Aggregate functions are an extension.
Note that there is no CREATE ROUTINE command.