Re: small exclusion constraints patch

On Sat, May 29, 2010 at 11:40 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Sat, May 29, 2010 at 6:11 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Or, to put it differently: if nobody's done that in the past twenty
>>> years, why is it likely to happen before 9.1?
>
>> Hmm.  Well suppose we bet a dollar on whether that will happen or not.
>>  In fact, if you promise not to read
>> http://archives.postgresql.org/pgsql-hackers/2010-05/msg01175.php I'll
>> make it two dollars.
>
> Yes, I've seen Jeff's example.  It's a cute hack but somehow I doubt
> that there is going to be a land rush to implement such things.
> Can you point to any pre-existing example where anyone actually asked
> for the ability to do that?

I've often wished for the ability to constrain a tale to hold just one
row, so I don't find that use case implausible at all. As to whether
Jeff's use case is a cute hack or something that people will really
want to do, I think the jury's still out on that one. But I don't
think we should make it not work unless we have a concrete reason, and
I haven't heard one yet.

--
Robert Haas
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