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Re: Fwd: [NOVICE] Trigger and Recursive Relation ?

From: "Nikolay Samokhvalov" <samokhvalov(at)gmail(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Fwd: [NOVICE] Trigger and Recursive Relation ?
Date: 2006-08-02 07:37:03
Message-ID: e431ff4c0608020037y45e6a7f8j2f0a387ef4ea780c@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-bugspgsql-novice
OK, then we should at least forbit making such things... Otherwise, it
seems to be smth like gotcha.

But look at this please:

"12) If <search condition> is specified, then the <search condition> is
evaluated for each row of T prior
invocation of any <triggered action> caused by the imminent or actual
deletion of any row of T."

Does Postgres work  this way? In the case of 'delete from tbl;' we
have search condition>=TRUE for all rows. If we evaluate it *before*
any other operation, we should mark  all rows to be deleted. I guess,
Postgres doesn't follow this logic..

Am I wrong?

P.S. BTW, look at the -novice list - he reports, that problem remains
even after dropping FK at all.

On 8/2/06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> "Nikolay Samokhvalov" <samokhvalov(at)gmail(dot)com> writes:
> > Is this a bug or not?
>
> I don't think so --- or perhaps better, this is a buggy trigger.
> he UPDATE in the trigger will supersede the base DELETE query for any
> rows that the UPDATE changes before the base DELETE has reached 'em.
> Essentially you've written an indeterminate system ...
>
>                         regards, tom lane
>


-- 
Best regards,
Nikolay

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