Re: ALTER TABLE ... NOREWRITE option

> -----Original Message-----
> From: pgsql-hackers-owner@postgresql.org [mailto:pgsql-hackers-
> owner@postgresql.org] On Behalf Of Andres Freund
> Sent: 06 December 2012 20:44
> To: Petr Jelinek
> Cc: 'Simon Riggs'; 'Robert Haas'; 'Dimitri Fontaine'; 'Josh Berkus';
pgsql-
> hackers@postgresql.org
> Subject: Re: [HACKERS] ALTER TABLE ... NOREWRITE option
> > > Event triggers get called *during* the ALTER TABLE. So if were not
> > > careful they see something thats not easy to handle.
> > >
> >
> > I thought the point of this was to call the trigger *before* anything
> > happens.
> 
> Just because the rewrite hasn't started yet, doesn't mean nothing else has
> been changed.
> 
> Note, I am not saying this is impossible or anything, the original point
drawn
> into question was that we need to be especially careful with choosing
> callsites and thats its not trivial to do right.
> 

Ok my assumption is that the event would be fired before ALTER actually did
anything, firing triggers while DDL is actually already being executed seems
like bad idea.

Regards
Petr Jelinek