On Mon, Apr 25, 2016 at 7:57 PM, Stephen Frost <sfrost@xxxxxxxxxxx> wrote:
David, Melvin,
* David G. Johnston (david.g.johnston@xxxxxxxxx) wrote:
> On Monday, April 25, 2016, Melvin Davidson <melvin6925@xxxxxxxxx> wrote:
> > I need clarification on allow_system_table_mods parameter
> > Per the documentation:
> > *Allows modification of the structure of system tables.* This is used by
> > initdb. This parameter can only be set at server start.
> >
> > However, attempting to modify pg_class to add another column fails with
> > "STATUS_ACCESS_VIOLATION" as below.
> > So either only certain system catalogs may be changed, or only certain
> > types of structure changes are allowed.
There might be some things about system catalogs you can modify, but
generally speaking, you can't add a column or otherwise change the
structure. System catalogs are represented in memory by C structures
(and more), so it's not too surprising that adding a column causes a
crash.
> If it's going to prevent the action it should be able to do so without
> crashing the server..and I doubt it's intended to be opinionated aside from
> covering all DDL. What little there is on Google seems to support this.
Sorry, but as a superuser, there's a lot of things you can do to crash
the server, this is just one way. The effort required to prevent
anything bad from happening when a user is running as a superuser is far
from trivial.
In short, no, you can't just add a column to pg_class via SQL, and I
don't think we're going to be very interested in trying to "fix" such
cases.
Thanks!
Stephen
Thank you Stephen.
Then could you please clarify exactly what structural mods are permitted by "Allows modification of the structure of system tables" ?
--
Melvin Davidson
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.![]()
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.
