Re: SQL-standard function body

On Tue, Jun 30, 2020 at 1:49 PM Peter Eisentraut
<peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
> This adds support for writing CREATE FUNCTION and CREATE PROCEDURE
> statements for language SQL with a function body that conforms to the
> SQL standard and is portable to other implementations.

With what other implementations is it compatible?

> The function body is parsed at function definition time and stored as
> expression nodes in probin. So at run time, no further parsing is
> required.
>
> However, this form does not support polymorphic arguments, because
> there is no more parse analysis done at call time.
>
> Dependencies between the function and the objects it uses are fully
> tracked.
>
> A new RETURN statement is introduced. This can only be used inside
> function bodies. Internally, it is treated much like a SELECT
> statement.
>
> psql needs some new intelligence to keep track of function body
> boundaries so that it doesn't send off statements when it sees
> semicolons that are inside a function body.
>
> Also, per SQL standard, LANGUAGE SQL is the default, so it does not
> need to be specified anymore.

Hmm, this all seems like a pretty big semantic change. IIUC, right
now, a SQL function can only contain one statement, but it seems like
with this patch you can have a block in there with a bunch of
statements, sorta like plpgsql. But probably you don't have all of the
functionality of plpgsql available. Also, the fact that you're doing
parsing earlier means that e.g. creating a table and inserting into it
won't work. Maybe that's fine. But it almost seems like you are
inventing a whole new PL....

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company