Re: Missing ColLabel tokens

Tom Lane writes:

> > (For the interested, the only other completely reserved tokens are TYPE
> > and AS.)
>
> I suspect we're stuck on that for AS. However, TYPE is actually allowed
> as a ColId, via the 'generic' production, so in reality it's not
> reserved.

I think this generic production might be a mistake. The productions go
like this:

generic ::= <ident> | TYPE

ColId ::= <generic> | ...

Generic ::= <generic>

ConstTypename ::= <Generic> | (SQL type names)

AexprConst ::= <ConstTypename> <Sconst> | ...

SimpleTypename ::= <ConstTypename> | ...

and then SimpleTypename is sort of a Typename.

This allows TYPE to be used as a type name! All three of the statements

select cast(42 as type);
select type 'xxx';
create table foo (a type);

fail with "ERROR: Unable to locate type name 'type' in catalog". Besides
this there are no other productions making use of <generic>.

I see this was introduced in gram.y 2.180, 2000-07-28, with a message of

Fix acceptance of PATH as a type and column name.
Note that this has changed some of the edge cases for what is accepted
as a type name and/or column id. Regression test passes, but more
tweaks may be coming...

which makes this look unintentional. TYPE could simply be under ColId and
<generic> would simply be IDENT.

Where's the harm? you might ask. I'm going to have to insert a special
case into my extract-keyword-categories-from-gram.y (and make a DocBook
table from it) tool. ;-)

--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/