Re: Update on tables when the row doesn't change

On 5/24/05, Sebastian Böck <sebastianboeck(at)freenet(dot)de> wrote:
> Martijn van Oosterhout wrote:
> > I'm sure I'm not the only one, but, what are you talking about? RULEs
> > are not really obvious so it would help if you could post an example of
> > what you mean...
> >
> > Have a nice day,
>
> Hi, I'm not really talking about rules.
>
> I'm talking about updates on *real* tables, and how to avoid
> unnecessary updates on these tables if the row doesn't change.
>
> The situation looks like this:
>
> I have a view which is a join of a lot of tables.
>
> I have lot of conditional ON UPDATE rules to that view that split one
> update to the view into updates on the underlying table. The condition
> of each rule is constructed in a way that the underlying table only
> gets an update if the corresponding values change.
>
> If I collapse all these rules into one conditional rule and pass all
> the updates to the underlying tables, I get a lot of unnecessary
> updates to these real tables, if the values don't change.
>
> Thats what I want to avoid.
>
> Sorry for not beeing that clear.
>
> Sebastian
>
>
And how are you preventing the rule execute the update if the field
has no change? That is way Martijn told you about showing the rule.

AFAIK, if you execute an update on a view that has a ON UPDATE rule
all the SQL ACTIONS specified for the rule will be perfomed INSTEAD OF
the original update

--
Atentamente,
Jaime Casanova
(DBA: DataBase Aniquilator ;)