Re: Use of systable_beginscan_ordered in event trigger patch

On Fri, Dec 14, 2012 at 2:00 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Thu, Dec 13, 2012 at 6:25 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> I suspect there are still ways to shoot yourself in the foot with a
>>> broken event trigger, but it's not quite as trivial as I thought.
>
>> I'm smart enough not to doubt you, but I'd sure appreciate a hint as
>> to what you're worried about before we start building more on top of
>> it. I don't want to sink a lot of work into follow-on commits and
>> then discover during beta we have to rip it all out or disable it. It
>> seems to me that if you can always drop an event trigger without
>> interference from the event trigger system, you should at least be
>> able to shut it off if you don't like what it's doing.
>
> I doubt that not firing on DROP EVENT TRIGGER, per se, will be
> sufficient to guarantee that you can execute such a drop. Even
> if that's true in the current state of the code, we're already
> hearing requests for event triggers on lower-level events, eg
> http://archives.postgresql.org/pgsql-hackers/2012-12/msg00314.php

Yep, true.

> Sooner or later there will be one somewhere in the code path involved
> in doing a heap_delete on pg_event_trigger, or one of the subsidiary
> catalogs such as pg_depend, or maybe one that just manages to fire
> someplace during backend startup, or who knows what.

Yeah. :-(

> Hence, I want a kill switch for all event triggers that will most
> certainly work, and the just-committed patch provides one.

I'm definitely not disputing the need for that patch.

--
Robert Haas
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