Re: delta relations in AFTER triggers

From: Marti Raudsepp <marti(at)juffo(dot)org>
To: Kevin Grittner <kgrittn(at)ymail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Amit Khandekar <amit(dot)khandekar(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, David Fetter <david(at)fetter(dot)org>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: delta relations in AFTER triggers
Date: 2014-09-03 20:55:00
Message-ID: CABRT9RBO3OrdbpA82mkSrzebsEvuvw8x7zAREKcYH36bPMJawQ@mail.gmail.com
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On Wed, Sep 3, 2014 at 10:49 PM, Kevin Grittner <kgrittn(at)ymail(dot)com> wrote:
> Marti Raudsepp <marti(at)juffo(dot)org> wrote:
>> The concept of "lightweight relations" that pop into existence when a
>> certain kind of trigger definition is used somewhere in the function
>> stack, without a CREATE TABLE, without being discoverable in
>> information_schema etc., I find needs some more justification than
>> I've seen in this thread. So far I've only heard that it's more
>> convenient to implement in the current PostgreSQL code base.
>
> It is required by the SQL standard.

I had a cursory read of the SQL 20nn draft and I don't get this
impression. The only place I could find discussing the behavior of
"transition tables" is in Foundation "4.39.1 General description of
triggers", which says:

"Special variables make the data in the transition table(s) available
to the triggered action. For a statement-level
trigger the variable is one whose value is a transition table."

There is no information about the scoping of such variables, so I
assume it refers to a regular locally scoped variable.

Did I miss something? Are you reading a different version of the spec?

Regards,
Marti

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