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Re: BUG #1676: Statment order in rules

From: Olleg Samoylov <olleg(at)mipt(dot)ru>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #1676: Statment order in rules
Date: 2005-05-20 09:07:32
Message-ID: 428DA8D4.8020809@mipt.ru (view raw or flat)
Thread:
Lists: pgsql-bugs
Tom Lane wrote:
> This isn't a bug.  The DELETE causes the a=0 row to disappear from the

I undestand.

When I got choice between rules and triggers, I looked carefully is
documantation, section "33.6. Rules versus Triggers". As I can see,
rules prefered, there are many examples, why rules better then triggers.
Only described advantage of triggers is using triggers as constraints.

But later I got bugs and submit #1447, #1610, #1676. All resolved as
"not a bug". IMHO this is due to lack of documentation, don't described
explicitly what disadvatages or unexpected "features" rules have. Well
#1676 looked strange, but can de derived from "33.3. Rules on INSERT,
UPDATE, and DELETE". As I can undestand, if rule fire several commands, 
command to change table of rule must be last. This is not explicitly 
documented. ALSO rules didn't designed so. Why?

As I begin undestand now, bug #1447 is consequence from "feature" #1676, 
isn't it? And can be avoided by changing ALSO rule to INSTEAD rule with 
command to modify table, implicitly existed in ALSO rule, in the last. 
This workaround must be documented. Or may be better change ALSO rule 
behaviour?

#1610 disconform documentation. Documentation or rules must be fixed. 
Fix rules prefered.

As I undestand from bug resolution, this "features" don't planed to be 
fixed. I add comments to documentation about this "features", but this 
is all, what I can. As I can undestand now, my comment in documentation 
for "feature" #1447 in section "33.6. Rules versus Triggers" is 
incorrect, but I can't remove it.

-- 
Olleg Samoylov

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