Обсуждение: plpgsql: can I use a variable in a DECLARE later whithin the DECLARE?

Hi,

In plpgsql, i'm trying to use a variable initialised in a DECLARE in
a later initialisation expression whithin the same DECLARE:

  DECLARE
    x int := 23;
    y int := x + 4
  BEGIN
   ...

Experiments suggest that it works, but the docs are silent about that.
Is this a good idea, or should I be more careful and do it in a nested
block?

(For Lispers: is that a let, or a let*? ;-)

Thanks & cheers
 - tomás

<tomas@tuxteam.de> writes:
> In plpgsql, i'm trying to use a variable initialised in a DECLARE in
> a later initialisation expression whithin the same DECLARE:

>   DECLARE
>     x int := 23;
>     y int := x + 4
>   BEGIN
>    ...

> Experiments suggest that it works, but the docs are silent about that.
> Is this a good idea, or should I be more careful and do it in a nested
> block?

I don't see any reason to foresee that it would break.

However, I notice that we don't actually have any regression tests
checking this.  scope_test() in plpgsql.sql checks an adjacent
question, but not exactly this one.  I'm a bit inclined now to go
add such a test.

            regards, tom lane

On Fri, Oct 29, 2021 at 10:04:31AM -0400, Tom Lane wrote:
> <tomas@tuxteam.de> writes:
> > In plpgsql, i'm trying to use a variable initialised in a DECLARE in
> > a later initialisation expression whithin the same DECLARE:
>
> >   DECLARE
> >     x int := 23;
> >     y int := x + 4
> >   BEGIN
> >    ...
>
> > Experiments suggest that it works, but the docs are silent about that.
> > Is this a good idea, or should I be more careful and do it in a nested
> > block?
>
> I don't see any reason to foresee that it would break.

Thanks :)

> However, I notice that we don't actually have any regression tests
> checking this.  scope_test() in plpgsql.sql checks an adjacent
> question, but not exactly this one.  I'm a bit inclined now to go
> add such a test.

Even more thanks.

After a long hiatus I have the luck to play again with PostgreSQL.
Let me say: you folks rock, seriously.

Cheers
 - t