From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Peter Eisentraut <peter_e(at)gmx(dot)net>, Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Check constraints on non-immutable keys |
Date: | 2010-06-30 23:03:36 |
Message-ID: | AANLkTimXKQqWC7pldR3nlft_Rr_vk58P_DmfAA_Zdj1q@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Wed, Jun 30, 2010 at 6:57 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
>> <kibo>
>> "The <search condition> shall simply contain a <boolean value
>> expression> that is retrospectively deterministic."
>
>> This is then defined in a rather complex manner that ends up disallowing
>> col > now() but allowing col < now().
>> </kibo>
>
> Oh, cute. Seems to have been added in SQL:2003. I guess somebody
> nagged them about wanting to be able to write CHECK(col <= now()).
> The detailed definition is amazingly laborious and yet limited, though,
> as it basically doesn't address the problem except for that specific
> case and close relatives.
Well, solving the problem in general is equivalent to the halting problem, so...
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2010-06-30 23:05:03 | Re: Keeping separate WAL segments for each database |
Previous Message | Tom Lane | 2010-06-30 22:57:50 | Re: Check constraints on non-immutable keys |