Jaime Casanova wrote:
On 5/24/05, Sebastian Böck <[EMAIL PROTECTED]> 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...
I attach some sample SQL (commented) to demonstrate the described
scenario:
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.
Sorry I don't understand what you mean.
What's wrong with:
CREATE OR REPLACE RULE upd AS ON UPDATE TO view
WHERE NEW.field = OLD.field DO INSTEAD NOTHING;
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
Ok thanks for the tip, but I alredy knew this ;)
But my original question remeins:
Why does Postgres perform updates to tables, even if the row doesn't
change at all?
Thanks
Sebastian
---------------------------(end of broadcast)---------------------------
TIP 2: you can get off all lists at once with the unregister command
(send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
