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.

With Regards,
Ashutosh Sharma
EnterpriseDB: *http://www.enterprisedb.com <http://www.enterprisedb.com>*