Re: UPDATE SET (a,b,c) = (SELECT ...) versus rules

Hi,

On 2014-06-14 15:35:33 -0400, Tom Lane wrote:
> Given that ON UPDATE rules are close to being a deprecated feature,
> it doesn't seem appropriate to work harder than this; and frankly
> I don't see how we could avoid multiple sub-select evaluations anyway,
> if the NEW references are in WHERE or other odd places.
>
> Another possible answer is to just throw a "not implemented" error;
> but that doesn't seem terribly helpful, and I think it wouldn't save
> a lot of code anyway.

I vote for throwing an error. This would make the rules about how rules
can be used safely even more confusing. I don't think anybody would be
helped by that. If somebody wrote a halfway sane ON UPDATE rule
(i.e. calling a function to do the dirty work) it wouldn't be sane
anymore if somebody starts to use the new syntax...

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services