Parallel SAFE information missing in CREATE OR REPLACE FUNCTION definition

Hi,

In PGSQL-9.6, if we create a function with PARALLEL clause and try displaying it's definition using "pg_get_functiondef" we see that the PARALLEL keyword used during function creation is missing.

Below are the steps to reproduce:

postgres=# CREATE FUNCTION add(integer, integer) RETURNS integer
postgres-# AS 'select $1 + $2;'
postgres-# LANGUAGE SQL
postgres-# PARALLEL SAFE
postgres-# RETURNS NULL ON NULL INPUT;
CREATE FUNCTION

postgres=# CREATE OR REPLACE FUNCTION increment(i integer) RETURNS integer AS $$
postgres$#         BEGIN
postgres$#                 RETURN i + 1;
postgres$#         END;
postgres$# $$ LANGUAGE plpgsql PARALLEL SAFE;
CREATE FUNCTION

postgres=# CREATE FUNCTION square_root(double precision) RETURNS double precision
AS 'dsqrt'
LANGUAGE internal
PARALLEL SAFE;
CREATE FUNCTION

postgres=# \df
                           List of functions
 Schema |    Name     | Result data type | Argument data types |  Type 
--------+-------------+------------------+---------------------+--------
 public | add         | integer          | integer, integer    | normal
 public | increment   | integer          | i integer           | normal
 public | square_root | double precision | double precision    | normal
(3 rows)

postgres=# SELECT  pg_get_functiondef('add'::regproc);
                   pg_get_functiondef                   
---------------------------------------------------------
 CREATE OR REPLACE FUNCTION public.add(integer, integer)+
  RETURNS integer                                       +
  LANGUAGE sql                                          +
  STRICT                                                +
 AS $function$select $1 + $2;$function$                 +
 
(1 row)

postgres=# SELECT  pg_get_functiondef('increment'::regproc);
                   pg_get_functiondef                  
--------------------------------------------------------
 CREATE OR REPLACE FUNCTION public.increment(i integer)+
  RETURNS integer                                      +
  LANGUAGE plpgsql                                     +
 AS $function$                                         +
         BEGIN                                         +
                 RETURN i + 1;                         +
         END;                                          +
 $function$                                            +
 
(1 row)

postgres=# SELECT  pg_get_functiondef('square_root'::regproc);
                       pg_get_functiondef                       
-----------------------------------------------------------------
 CREATE OR REPLACE FUNCTION public.square_root(double precision)+
  RETURNS double precision                                      +
  LANGUAGE internal                                             +
 AS $function$dsqrt$function$                                   +
 
(1 row)


RCA: The proparallel information for a function is not considered while preparing its definition inside pg_get_functiondef().

Solution: Add a  check for the proparallel flag inside pg_get_functiondef() and based on the value in proparallel flag, store the parallel {safe | unsafe | restricted} info in the buffer  that holds the function definition. PFA patch to fix the issue.