Re: Return of INSTEAD rules

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От Bruce Momjian
Тема Re: Return of INSTEAD rules
Дата
Msg-id 200210041659.g94GxSS20072@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: Return of INSTEAD rules  (Manfred Koizar <mkoi-pg@aon.at>)
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Manfred Koizar wrote:
> On Thu, 3 Oct 2002 22:21:27 -0400 (EDT), Bruce Momjian
> <pgman@candle.pha.pa.us> wrote:
> >so I propose we handle
> >INSTEAD rules this way:  that we return the oid and tuple count of the
> >last INSTEAD rule query with a tag matching the main query.  
> 
> Bruce, this won't work for this example
> 
> >>     CREATE RULE visible_delete AS     -- DELETE rule
> >>     ON DELETE TO visible 
> >>     DO INSTEAD 
> >>         COUNT UPDATE table3
> >>         SET deleted = 1
> >>         WHERE pk = old.pk;
> 
> because here we don't have a rule query with a matching tag.  Same
> applies for

True, but because we have said we are going to return the tag of the
original command, I don't think we have anything valid to return in this
case to match the tag.

> >>     CREATE RULE v_update AS     -- UPDATE rule
> >>     ON UPDATE TO v 
> >>     DO INSTEAD NOTHING;

This is OK because the default is return zeros.

> I wrote:
> >> One argument against automatically "don't count non-INSTEAD rules and
> >> count the last statement in INSTEAD rules"
> 
> Seems I introduced a little bit of confusion here by argueing against
> something that has never been proposed before.  Funny, that this
> non-existent proposal is now seriously discussed :-(
> 
> Has the idea of extending the syntax to explicitly mark queries as
> COUNTed already been rejected?  If yes, I cannot help here.  If no, I

Well, I am hoping to find something that was automatic.  If we do our
best, and we still get complains, we can add some syntax.  I am
concerned that adding syntax is just over-designing something that isn't
necessary.

> keep telling you that this approach can emulate most of the other
> possible solutions still under discussion.
> 
> Bruce wrote:
> >If there is more than one matching tag in
> >the INSTEAD rule, the user has the option to place the query he wants
> >for the return at the end of the rule.
> 
> Are you sure this is always possible without unwanted side effects?

I am sure it isn't always possible, but let's do our best and see how
people react.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
359-1001+  If your life is a hard drive,     |  13 Roberts Road +  Christ can be your backup.        |  Newtown Square,
Pennsylvania19073
 


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