Re: to_regtype() Raises Error

On 2023-09-17 21:58, David G. Johnston wrote:
> ambiguity possible when doing that though:
>
> create type "interval second" as (x int, y int);
> select to_regtype('interval second'); --> interval

Not ambiguity really: that composite type you just made was named
with a single <delimited identifier>, which is one token. (Also,
being delimited makes it case-sensitive, and always distinct from
an SQL keyword; consider the different types char and "char". Ah,
that SQL committee!)

The argument to regtype there is a single, case-insensitive,
<regular identifier>, a <separator>, and another <regular identifier>,
where in this case the first identifier happens to name a type, the
second one happens to be a typmod, and the separator is rather
simple as <separator> goes.

In this one, both identifiers are part of the type name, and the
separator a little more flamboyant.

select to_regtype('character /* hi!
am I part of the type name? /* what, me too? */ ok! */ -- huh!
varying');
to_regtype
-------------------
character varying

As the backend already has one parser that knows all those
lexical and grammar productions, I don't imagine it would be
very appealing to have a second implementation of some of them.
Obviously, to_regtype could add some simplifying requirements
(like "only whitespace for the separator please"), but as you
see above, it currently doesn't.

Regards,
-Chap