Re: return two elements - Mailing list pgsql-general

I don't know that it happens with my email I will change the email of my subscription.

The examples are very interesting for my, and Alvaro Herrera's comments too.

In reference to INOUT/OUT params and return a set I have a doubt: I will be able to return a set of  table row type and return INOUT/OUT params?. For example,

CREATE TABLE foo_table
(
        id int4;
        dsc varchar(20;
);

CREATE FUNCTION foo(INOUT y integer, OUT z integer) RETURNS SETOF foo_table AS $$
DECLARE
        row foo_table%ROWTYPE;
BEGIN
        z := y + 1;
        y := 33;

        row.id := 1;
        row.dsc := 'dsc 1';
        retrun next row;

        row.id := 2;
        row.dsc := 'dsc 2';
        retrun next row;

        return;
END;
$$ LANGUAGE plpgsql;
 
SELECT * FROM foo(1,2);
 id | dsc 
----+-------
 1  |  dsc 1
 2  |  dsc 2

In the example return next works like now and in addition function has a INOUT/OUT params that acts as host variables for interact with others functions.

pere

-----Mensaje original-----
De: Alvaro Herrera [mailto:alvherre@surnet.cl]
Enviado el: miércoles 8 de junio de 2005 17:53
Para: Michael Fuhr
CC: Tom Lane; pgsql-general@postgresql.org
Asunto: Re: [GENERAL] return two elements

I dropped prr@hosppal.es from the Cc: because that account has serious
issues.

On Wed, Jun 08, 2005 at 08:16:32AM -0600, Michael Fuhr wrote:
> On Wed, Jun 08, 2005 at 01:28:56AM -0400, Tom Lane wrote:
> > Alvaro Herrera <alvherre@surnet.cl> writes:
> > > Hmm, be aware that you can't return a set if you have OUT/INOUT
> > > parameters.
> >
> > ?  News to me --- what are you worried about exactly?
> >
> > It's surely possible that our idea of what this means is different
> > from Oracle's, but we ought to take a close look before the semantics
> > get set in stone by a release ...

My point is that Oracle and others, you can have an OUT parameter to
return, say a number, and additionally a set like those returned with
RETURN NEXT.  And both things are independent.

> The following example works in HEAD:
>
> CREATE FUNCTION foo(INOUT y integer, OUT z integer) RETURNS SETOF record AS $$
> BEGIN
>     y := y + 1; z := y + 2; RETURN NEXT;
>     y := y + 1; z := z + 3; RETURN NEXT;
>     y := y + 1; z := z + 4; RETURN NEXT;
> END;
> $$ LANGUAGE plpgsql;
>
> SELECT * FROM foo(1);
>  y | z 
> ---+----
>  2 |  4
>  3 |  7
>  4 | 11
> (3 rows)

Yeah, but if you do that, you can't use the OUT parameter separately.
My point is that something like this doesn't work:

CREATE FUNCTION foo (OUT y) RETURNS SETOF int LANGUAGE plpgsql AS $$
DECLARE
  z INT;
BEGIN
  y := 4;
  FOR z IN 1 .. 3 LOOP
    RETURN NEXT z;
  END LOOP;
END;
$$

Now, this approach has a problem, and it's where do you save the value
of y?  We have no "host variables."  This is exactly the reason Tom
punted and made it return OUT/INOUT params in the result set, at the
same time prohibiting it from receiving further output.

--
Alvaro Herrera (<alvherre[a]surnet.cl>)
"Llegará una época en la que una investigación diligente y prolongada sacará
a la luz cosas que hoy están ocultas" (Séneca, siglo I)

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