Re: ALTER TABLE ... NOREWRITE option

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/
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