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

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

> Pavel Stehule <pavel.stehule@gmail.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
>