Re: Converting to identity columns with domains on PK columns

On 7/5/19 3:32 PM, Tom Lane wrote:
> Adrian Klaver <adrian.klaver@aklaver.com> writes:
>> On 7/5/19 1:49 PM, PegoraroF10 wrote:
>>> Sorry, the example I was thinking was this one, which works on Firebird,
>>> using its way of writing, obviously.
>>> create function myproc(id integer) returns I32 language sql as 'select $1';
>>>
>>> On postgres ERROR: return type mismatch in function declared to return i32
>>> What I mean is that Firebird sees I32 and integer as the same, Postgres
>>> doesn´t.
> 
>> Yeah, but if you reverse the casting you did in your first example it works:
>> create function myproc(id integer) returns I32 language sql as 'select
>> $1::i32';
>> CREATE FUNCTION
> 
> Yeah.  This isn't an inherent property of Postgres, it's just that
> SQL-language functions aren't defined to provide any implicit casting
> of their results.  The given expression must yield exactly the declared
> function result type.

Aah:

CREATE OR REPLACE FUNCTION public.domain_test(id integer)
  RETURNS i32
  LANGUAGE plpgsql
AS $function$
BEGIN
     RETURN id;
END;
$function$
;

test=> select domain_test(5);
  domain_test
-------------
            5

test=> select pg_typeof(domain_test(5));
  pg_typeof
-----------
  i32
(1 row)

So it works in plpgsql.


> 
> Most other places in PG are laxer and will automatically perform
> implicit (and maybe assignment) casts for you.  I don't remember
> offhand whether there are good reasons for SQL functions to be
> picky about this or it's just a shortage of round tuits.  I have
> a vague feeling that there might be some compatibility issues
> in there, though.
> 
>             regards, tom lane
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com