From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
---|---|
To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: ALTER TABLE ... NOREWRITE option |
Date: | 2012-12-06 18:42:22 |
Message-ID: | CA+U5nMJVh2anemhC7LbM_SB_y1Xy6cCw+pvh7w_vAbXXbREzig@mail.gmail.com |
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Lists: | pgsql-hackers |
On 6 December 2012 18:31, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On 2012-12-06 18:21:09 +0000, Simon Riggs wrote:
>> On 6 December 2012 00:46, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> > On Wed, Dec 5, 2012 at 6:45 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> >> Yes, but it is also the trigger writers problem.
>> >
>> > Maybe to some degree. I don't think that a server crash or something
>> > like a block-read error is ever tolerable though, no matter how silly
>> > the user is with their event trigger logic. If we go down that road
>> > it will be impossible to know whether errors that are currently
>> > reliable indicators of software or hardware problems are in fact
>> > caused by event triggers. Of course, if an event trigger causes the
>> > system to error out in some softer way, that's perfectly fine...
>>
>> How are event triggers more dangerous than normal triggers/functions?
>
> Normal triggers aren't run when the catalog is in an in-between state
> because they aren't run while catalog modifications are taking place.
"in-between state" means what? And what danger do you see?
If its just "someone might write bad code" that horse has already
bolted - functions, triggers, executor hooks, operators, indexes etc
I don't see any difference between an event trigger and these statements...
BEGIN;
ALTER TABLE x ...;
SELECT somefunction();
ALTER TABLE y ...;
COMMIT;
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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