Re: Sanding down some edge cases for PL/pgSQL reserved words

ne 8. 6. 2025 v 23:49 odesílatel Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> napsal:

> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> > Is there some description of what keywords should be reserved? If I
> > remember correctly, the scanner was changed more times, and maybe more
> > reserved keywords are not necessary.
>
> Per the comment in pl_scanner.c:
>
> * We try to avoid reserving more keywords than we have to; but there's
> * little point in not reserving a word if it's reserved in the core
> grammar.
> * Currently, the following words are reserved here but not in the core:
> * BEGIN BY DECLARE EXECUTE FOREACH IF LOOP STRICT WHILE
>
> This patch gets rid of EXECUTE and STRICT, but the others are harder
> to de-reserve. I think most of the rest are there because they can
> follow a block or loop label, and the same comment observes
>
> * (We still have to reserve initial keywords that might follow a block
> * label, unfortunately, since the method used to determine if we are at
> * start of statement doesn't recognize such cases.
>

Looks so block label is a problem, but loop label not - and then BEGIN
DECLARE WHEN is really required reserved world
by gram.y

Maybe these comments are a little bit obsolete. Probably is not a good idea
to make unreserved words keywords used
as read_sql_xxxx delimiter: WHEN, LOOP, WHILE, INTO, USING, IN, FROM, and
maybe some other. This is probably
main reason why PL/pgSQL has these keywords marked as reserved.

Maybe there should be a new assert, that checks so the keywords used as
delimiters are reserved keywords.

I checked the list of reserved words of Ada language or PL/SQL language and
we are significantly different.

I can imagine two situations.

a) current state + Tom's patch that reports so keywords are reserved

b) ignore the keyword after the "dot" symbol, and allow the reserved
keyword as a record field without limits. SQL now allows using a lot of
keywords as labels without
necessity of using AS or double quoting.

Both variants can work well I think - a) is more strict, zero invasive, b)
is more user friendly, but small typo can hide some problems.

What do you think about it?

Regards

Pavel

>
> regards, tom lane
>