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Re: Missing ColLabel tokens

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Missing ColLabel tokens
Date: 2001-01-04 22:33:13
Message-ID: Pine.LNX.4.30.0101042312470.1245-100000@peter.localdomain (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
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

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