DROP PROCEDURE — remove a procedure
DROP PROCEDURE [ IF EXISTS ]name[ ( [ [argmode] [argname]argtype[, ...] ] ) ] [, ...] [ CASCADE | RESTRICT ]
   DROP PROCEDURE removes the definition of one or more
   existing procedures. To execute this command the user must be the
   owner of the procedure(s). The argument types to the
   procedure(s) usually must be specified, since several different procedures
   can exist with the same name and different argument lists.
  
IF EXISTSDo not throw an error if the procedure does not exist. A notice is issued in this case.
nameThe name (optionally schema-qualified) of an existing procedure.
argmode
      The mode of an argument: IN, OUT,
      INOUT, or VARIADIC.  If omitted,
      the default is IN (but see below).
     
argname
      The name of an argument.
      Note that DROP PROCEDURE does not actually pay
      any attention to argument names, since only the argument data
      types are used to determine the procedure's identity.
     
argtypeThe data type(s) of the procedure's arguments (optionally schema-qualified), if any. See below for details.
CASCADEAutomatically drop objects that depend on the procedure, and in turn all objects that depend on those objects (see Section 5.14).
RESTRICTRefuse to drop the procedure if any objects depend on it. This is the default.
If there is only one procedure of the given name, the argument list can be omitted. Omit the parentheses too in this case.
   In PostgreSQL, it's sufficient to list the
   input (including INOUT) arguments,
   because no two routines of the same name are allowed to share the same
   input-argument list.  Moreover, the DROP command
   will not actually check that you wrote the types
   of OUT arguments correctly; so any arguments that
   are explicitly marked OUT are just noise.  But
   writing them is recommendable for consistency with the
   corresponding CREATE command.
  
   For compatibility with the SQL standard, it is also allowed to write
   all the argument data types (including those of OUT
   arguments) without
   any argmode markers.
   When this is done, the types of the procedure's OUT
   argument(s) will be verified against the command.
   This provision creates an ambiguity, in that when the argument list
   contains no argmode
   markers, it's unclear which rule is intended.
   The DROP command will attempt the lookup both ways,
   and will throw an error if two different procedures are found.
   To avoid the risk of such ambiguity, it's recommendable to
   write IN markers explicitly rather than letting them
   be defaulted, thus forcing the
   traditional PostgreSQL interpretation to be
   used.
  
   The lookup rules just explained are also used by other commands that
   act on existing procedures, such as ALTER PROCEDURE
   and COMMENT ON PROCEDURE.
  
   If there is only one procedure do_db_maintenance,
   this command is sufficient to drop it:
DROP PROCEDURE do_db_maintenance;
Given this procedure definition:
CREATE PROCEDURE do_db_maintenance(IN target_schema text, OUT results text) ...
any one of these commands would work to drop it:
DROP PROCEDURE do_db_maintenance(IN target_schema text, OUT results text); DROP PROCEDURE do_db_maintenance(IN text, OUT text); DROP PROCEDURE do_db_maintenance(IN text); DROP PROCEDURE do_db_maintenance(text); DROP PROCEDURE do_db_maintenance(text, text); -- potentially ambiguous
However, the last example would be ambiguous if there is also, say,
CREATE PROCEDURE do_db_maintenance(IN target_schema text, IN options text) ...
This command conforms to the SQL standard, with these PostgreSQL extensions:
The standard only allows one procedure to be dropped per command.
The IF EXISTS option is an extension.
The ability to specify argument modes and names is an extension, and the lookup rules differ when modes are given.