Re: [HACKERS] subqueries in check

2005-01-09 Thread Alvaro Herrera
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 ([EMAIL PROTECTED])
No single strategy is always right (Unless the boss says so)
  (Larry Wall)

---(end of broadcast)---
TIP 5: Have you checked our extensive FAQ?

   http://www.postgresql.org/docs/faqs/FAQ.html


[HACKERS] subqueries in check

2005-01-07 Thread Jaime Casanova
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

_
Do You Yahoo!?
Información de Estados Unidos y América Latina, en Yahoo! Noticias.
Visítanos en http://noticias.espanol.yahoo.com

---(end of broadcast)---
TIP 9: the planner will ignore your desire to choose an index scan if your
  joining column's datatypes do not match