| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> |
| Cc: | "Darren Duncan *EXTERN*" <darren(at)darrenduncan(dot)net>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: adding support for zero-attribute unique/etc keys |
| Date: | 2013-03-25 13:27:40 |
| Message-ID: | 11040.1364218060@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> writes:
> Darren Duncan wrote:
>> I propose that this be generalized so that constraints may instead be nullary,
>> that is, range over zero or more attributes/columns instead.
> Since an imagined zero-column query would have an empty set of
> result columns, you could with equal force argue that these columns
> satisfy the condition or not, because the members of the empty
> set have all the properties you desire.
The semantics of a zero-column foreign key seem even less well
defined.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2013-03-25 13:30:00 | Re: [PATCH] Exorcise "zero-dimensional" arrays (Was: Re: Should array_length() Return NULL) |
| Previous Message | Bruce Momjian | 2013-03-25 13:25:44 | Re: Enabling Checksums |