Re: ALTER TABLE ... NOREWRITE option

On 6 December 2012 18:31, Andres Freund <andres@2ndquadrant.com> wrote:
> On 2012-12-06 18:21:09 +0000, Simon Riggs wrote:
>> On 6 December 2012 00:46, Robert Haas <robertmhaas@gmail.com> wrote:
>> > On Wed, Dec 5, 2012 at 6:45 PM, Simon Riggs <simon@2ndquadrant.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