Re: Object-Relational table design question

On June 17, 2003 12:23 pm, Josh Berkus wrote:
> Personally, I'm not a fan of inherited tables; I think they muddy up
> the relationality of SQL without providing any additional

We actually are doing what the original poster is in the process of 
doing; we have an ISP billing system based on postgresql. I have to 
agree with the above. We actually did use inheritence for a few things 
(though not for account definitions), and I've always found it somewhat 
of a pain. Especially when pg_dump was broken and corrupted the 
database on restore... I believe this is fixed now, but I can't see the 
benefit of the complication, whereas it does make the relationships 
more murky as described above.

>     JOIN webhosting ON service.id = webhosting.service

This would work though it's not very scaleable. Our current system makes 
all elements of a service into what we call an 'attribute'. The 
attributes are defined in a table, and attached to each account type, 
and turned on or off, and twiddled with various definitions such as 
term/period billing, etc. This makes it relatively easy to add new 
services... just add another entry in the account attributes table, 
whereas with hard coded joins above, if you add more services you're 
going to have to edit all of your code where joins take place.

So the billing job, for example, if you want a list of services that a 
customer's account has:

SELECT * FROM account_attribute 
WHERE account_type=customer.account_type
AND bill_mode>0;

(We go even further and do resource based accounting in yet another 
relation which references the attributes... it's a bit complicated, but 
I think its proving quite flexible so far, and cleaner than using 
inheritance).

-- 
Tim Middleton | Cain Gang Ltd | But the trouble was that my hysterical 
fit
x@veX.net     | www.Vex.Net   | could not go on for ever. --Dost (NFTU)