From: | Thom Brown <thom(at)linux(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>, pgsql-hackers(at)postgresql(dot)org, Andres Freund <andres(at)anarazel(dot)de> |
Subject: | Re: Command Triggers, patch v11 |
Date: | 2012-03-09 15:09:04 |
Message-ID: | CAA-aLv6-uZ+oNDzRAc9XrH8M6RJgSi7+VviozjoiCM5FNz07tg@mail.gmail.com |
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On 9 March 2012 15:05, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Fri, Mar 9, 2012 at 9:22 AM, Thom Brown <thom(at)linux(dot)com> wrote:
>>> Sorry, I meant any command trigger. It's because none of the commands
>>> can be run on a standby, so the triggers don't seem appropriate.
>
>> I'm not convinced. Right now, it's fairly useless - all the triggers
>> could possibly do is throw an error, and an error is going to get
>> thrown anyway, so it's only a question of which error message the user
>> will see. But we discussed before the idea of adding a capability for
>> BEFORE triggers to request that the actual execution of the command
>> get skipped, and then it's possible to imagine this being useful.
>
> Um, surely the "you can't do that in a read-only session" error is going
> to get thrown long before the command trigger could be called?
Yes, at the moment that's the case. I said that this wasn't the case
for utility commands but I've noticed the message is different for
those:
ERROR: cannot execute VACUUM during recovery
vs
ERROR: cannot execute CREATE TABLE in a read-only transaction
So my complaint around that was misleading and wrong.
--
Thom
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