Re: Practice advice for use of %type in declaring a subprogram's formal arguments

On 3/10/23 15:28, Bryn Llewellyn wrote:
> I'm thinking about "language plpgsql" subprograms—but I expect that my
> question can be generalized to cover "language sql" too.
>
> The payload for "create [or replace]" for a "language plpgsql" subprogram
> specifies various metadata elements like its qualified name, list of
> formal arguments and their modes and datatypes, "security invoker/definer"
> and so on together with the enquoted actual PL/pgSQL source text.
>
> When the DDL succeeds, the PL/pgSQL source text is recorded verbatim in
> "pg_proc". But the meaning of everything else is parsed out and
> represented as individual fields in "pg_proc" and other tables like
> "pg_namespace". This is reflected by the canonical form that "\sf" uses,
> for example:
>
> create table s.t(k integer primary key, v integer);
>
> create procedure s.p(k_in in t.k%type, v_in t.v%type)
>   language plpgsql
> as $body$
> begin
>  /* ... */
> end;
> $body$
>
> \sf s.p
>
> This is the output:
>
> CREATE OR REPLACE PROCEDURE s.p(k_in integer, v_in integer)
>  LANGUAGE plpgsql
> AS $procedure$
> begin
>  /* ... */
> end;
> $procedure$
>
> This shows that my use of "%type"was consumed at "create" time and then
> recorded in the catalog as what it translated to. The consequence is that
> if the table is dropped and re-created thus:

Here's what happens when you use domains.  The first thing I (pun intended)
noticed are the two NOTICE messages.  You might have noticed them if your
log_min_messages level was high enough.

CREATE DOMAIN
postgres=# create domain d_counting_ints integer check (value > 0);
CREATE DOMAIN
postgres=#
                      ^
postgres=# drop table if exists foo;
NOTICE:  table "foo" does not exist, skipping
DROP TABLE
postgres=# create table foo(pk d_pk, c d_counting_ints);
CREATE TABLE
postgres=#
postgres=# create procedure mypro(p_pk foo.pk%type, p_cnt foo.c%type)
postgres-#     language plpgsql
postgres-# as $body$
postgres$# begin
postgres$#    raise notice '% %', p_pk, p_cnt;
postgres$# end;
postgres$# $body$
postgres-# ;
NOTICE:  type reference foo.pk%TYPE converted to d_pk
NOTICE:  type reference foo.c%TYPE converted to d_counting_ints
CREATE PROCEDURE
postgres=#
postgres=# \sf mypro
CREATE OR REPLACE PROCEDURE public.mypro(p_pk d_pk, p_cnt d_counting_ints)
 LANGUAGE plpgsql
AS $procedure$
begin
   raise notice '% %', p_pk, p_cnt;
end;
$procedure$

--
Born in Arizona, moved to Babylonia.