On Wed, 2004-02-11 at 22:30, Tom Lane wrote:
> Gavin Sherry <swm@linuxworld.com.au> writes:
> > There have been a few discussions about triggers on system tables in
> > the past and the problems with such triggers seem to be:
>
> I think the killer problem is that we couldn't allow triggers on system
> tables to do very much. By definition, the database is in an inconsistent
> state if we are in the middle of updating system tables. We can't allow
> arbitrary bits of SQL to run then.
Yes, the internal calls from one command to another make this tricky --
but the return Tag is set very early for the statement. Could the Before
trigger for system commands (CREATE, ALTER, etc.) not be kicked of in
the same area as the tag is set?