RE: Use a rule or a transaction

Create a trigger on module before update or insert. The philosophy of
postgres is to create a trigger based on a function previously created. 
Take a look at the docs, the part on procedural languages. The book
from Momjian has one or two examples on triggers creation.

--
Jesus Aneiros Sosa
mailto:aneiros@jagua.cfg.sld.cu
http://jagua.cfg.sld.cu/~aneiros

On Tue, 15 Aug 2000, Madel, Kurt wrote:

> 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>
> <|> antoiner@hansonpublications.com <|    don't mix. Never drink   |
>  >\    antoiner@edmarketing.com      >\         and derive.       /<
>