ALTER FUNCTION $name$ [ ( [ { [ $routine_argmode$ ] [ $argname$ ] $argtype$ } [ , ... ] ] ) ]
    $action$ [ ... ] [ RESTRICT ]

ALTER FUNCTION $name$ [ ( [ { [ $routine_argmode$ ] [ $argname$ ] $argtype$ } [ , ... ] ] ) ]
    RENAME TO $new_name$

ALTER FUNCTION $name$ [ ( [ { [ $routine_argmode$ ] [ $argname$ ] $argtype$ } [ , ... ] ] ) ]
    OWNER TO { $new_owner$ | CURRENT_ROLE | CURRENT_USER | SESSION_USER }

ALTER FUNCTION $name$ [ ( [ { [ $routine_argmode$ ] [ $argname$ ] $argtype$ } [ , ... ] ] ) ]
    SET SCHEMA $new_schema$

ALTER FUNCTION $name$ [ ( [ { [ $routine_argmode$ ] [ $argname$ ] $argtype$ } [ , ... ] ] ) ]
    [ NO ] DEPENDS ON EXTENSION $extension_name$

where $action$ is:

CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT |
    IMMUTABLE | STABLE | VOLATILE |
    [ NOT ] LEAKPROOF |
    [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER |
    PARALLEL { UNSAFE | RESTRICTED | SAFE } |
    COST $execution_cost$ |
    ROWS $result_rows$ |
    SUPPORT $support_function$ |
    SET $configuration_parameter$ { TO | = } { $value$ | DEFAULT } |
    SET $configuration_parameter$ FROM CURRENT |
    RESET $configuration_parameter$ |
    RESET ALL