Re: DO INSTEAD and conditional rules

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: David Wheeler <david(at)kineticode(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Neil Conway <neilc(at)samurai(dot)com>, Jan Wieck <JanWieck(at)yahoo(dot)com>
Subject: Re: DO INSTEAD and conditional rules
Date: 2005-04-26 15:55:58
Message-ID: 2542.1114530958@sss.pgh.pa.us
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David Wheeler <david(at)kineticode(dot)com> writes:
> On Apr 25, 2005, at 11:37 PM, Tom Lane wrote:
>> (I have been thinking more and more that we should consider a wholesale
>> redesign of the rule mechanism, because it sure seems not to answer the
>> needs/expectations of a lot of people out there.

> I think that people are likely to confuse rules and triggers. The other
> issue is that they are not documented in such a way as to make them
> simple to understand. But beyond that, although I like Neil's
> suggestion better, rules work pretty well for what I need them for--the
> ability to INSERT, UPDATE, or DELETE on a view.

Well, they handle simple situations OK, but we keep seeing people get
burnt as soon as they venture into interesting territory. For instance,
if the view is a join, you can't easily make a rule that turns a delete
into deletions of both joined rows. And you'll get burnt if you try to
insert any volatile functions, because of the multiple-evaluation issue.
Etc.

Like I said, I don't have a better idea. Just a vague feeling of
dissatisfaction.

regards, tom lane

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