RE: Use a rule or a transaction

Hello Antoine,

I thought that triggers only worked for one table at a time.  In this case,
I want the class.size incremented and checked for maxsize when I perform an
update or insert on the module table.  I was under the impression that a
trigger would only work if I was performing an insert or update on the same
table that I wanted the trigger to act on.

Please let me know if I am way off in regards to triggers.

thanks,
Kurt

-----Original Message-----
From: Antoine Reid [mailto:antoiner@hansonpublications.com]
Sent: Tuesday, August 15, 2000 2:43 PM
To: Madel, Kurt
Cc: pgsql-sql@postgresql.org
Subject: Re: [SQL] Use a rule or a transaction


On Tue, Aug 15, 2000 at 01:57:17PM -0400, Madel, Kurt wrote:
> Hello,
> 
> I am creating a web based (using php) class registration database with
three
> tables directly effected by the registration process:

[snip]

> My question is, would it be better (faster) to use rules or to use a
> transaction.

How about using triggers?  I have used pl/pgsql triggers in the past to do
similar things.  I was not checking a maximum but definitely was keeping a
reference count.  What you want is a trigger that increments on insert,
decrement on delete, and on update, IF the id changed, decrement the old
one, increment the new one..  I suspect you could also have another trigger,
on update on class, that would abort the transaction if class.size ever
becomes bigger than maxsize..

I can't really comment on performance though.....

> Is there a faster way to do this with rules or a better way to do it
> otherwise.
> 
> TIF,
> Kurt

Hope it helps
Antoine

-- o          Antoine Reid             o>    Alcohol and calculus   <o>
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