| Lists: | pgsql-hackers |
|---|
| From: | Jaime Casanova <systemguards(at)yahoo(dot)com> |
|---|---|
| To: | pgsql hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | subqueries in check |
| Date: | 2005-01-08 05:06:58 |
| Message-ID: | 20050108050658.44793.qmail@web50001.mail.yahoo.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Lists: | pgsql-hackers |
Hi,
i was looking at the unsuported features in the RC4
docs and found this:
F671| Enhanced integrity management| Subqueries in
CHECK| intentionally omitted
Why is it *intentionally omitted*?
Is it to hard? or has some side-effects?
just a question!
regards,
Jaime Casanova
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| From: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
|---|---|
| To: | Jaime Casanova <systemguards(at)yahoo(dot)com> |
| Cc: | pgsql hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: subqueries in check |
| Date: | 2005-01-09 16:14:57 |
| Message-ID: | 20050109161457.GE4194@dcc.uchile.cl |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Lists: | pgsql-hackers |
On Fri, Jan 07, 2005 at 11:06:58PM -0600, Jaime Casanova wrote:
Jaime,
> i was looking at the unsuported features in the RC4
> docs and found this:
>
> F671| Enhanced integrity management| Subqueries in CHECK| intentionally omitted
>
> Why is it *intentionally omitted*?
> Is it to hard? or has some side-effects?
Because it's too expensive to check. If you have a CHECK using a SELECT
against a second table, you should re-verify the SELECT every time the
second table suffers an UPDATE, INSERT or DELETE.
The user can replace the CHECK with a foreign key or a trigger, so there
is no loss of functionality.
--
Alvaro Herrera (<alvherre[(at)]dcc(dot)uchile(dot)cl>)
"No single strategy is always right (Unless the boss says so)"
(Larry Wall)