Re: UPDATE SET (a,b,c) = (SELECT ...) versus rules - Mailing list pgsql-hackers

From Andres Freund
Subject Re: UPDATE SET (a,b,c) = (SELECT ...) versus rules
Date
Msg-id 20140614194508.GE6763@awork2.anarazel.de
Whole thread Raw
In response to UPDATE SET (a,b,c) = (SELECT ...) versus rules  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: UPDATE SET (a,b,c) = (SELECT ...) versus rules  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
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



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