Re: CALL optional in PL/pgSQL

On Fri, Mar 2, 2018 at 2:01 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
>> 2018-03-01 5:51 GMT+01:00 Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com
>>> This seems to be a popular issue when porting from PL/SQL, so I'll throw
>>> it out here for discussion. Apparently, in PL/SQL you can call another
>>> procedure without the CALL keyword. Here is a patch that attempts to
>>> implement that in PL/pgSQL as well. It's not very pretty.
>
>> The CALL is not optional in PL/SQL - I was surprised - it is required in
>> some environments, and it should not be used in other (like PL/SQL)

It's not required in a PL/SQLl block, see
<https://www.tutorialspoint.com/plsql/plsql_procedures.htm>

This is hardly surprising given PL/SQL's Ada roots. This is exactly
how Ada allows procedure calls.

>
> I think this is an actively bad idea. It introduces an inherent ambiguity
> into the grammar; for instance
>
> PERFORM (2);
>
> now has two valid interpretations. The only way to resolve that is with
> heuristics or treating a bunch more words as reserved keywords, neither of
> which are appetizing. (I didn't look to see which way Peter did it, but
> his description of his patch as "not very pretty" doesn't fill me with
> happiness.) And it would likely cause headaches down the road whenever
> we attempt to add new syntax to plpgsql.
>
> I think we should reject the idea.

Well, the upside would be increased Oracle compatibility. I don't
think that's worthless.

I haven't dug deeply into it, but Peter's patch didn't look
desperately ugly to me at first glance.

Even though it's a tiny patch this seems like next release material at best.

>
>>> Also, I think PL/SQL allows you to call a procedure with no arguments
>>> without parentheses. I have not implemented that. I think it could be
>>> done, but it's not very appealing.
>
>> I don't like this feature.
>
> This idea is even worse in terms of the amount of syntax space it will
> occupy, again for zero functional benefit.
>

If we were going to do it then we should be consistent about it and
also allow parameter-less function calls to skip the parentheses. But
anyway none of that is currently proposed so let's save the argument
for the time when it is :-)

cheers

andrew

--
Andrew Dunstan https://www.2ndQuadrant.com
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