Re: Truncation of mapped catalogs (whether local or shared) leads to server crash

Hi,

On Tue, Jun 18, 2024 at 8:25 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> writes:
> > On Tue, Jun 18, 2024 at 7:50 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> I think the assertion you noticed is there because the code path gets
> >> traversed during REINDEX, which is an operation we do support on
> >> system catalogs. I have zero interest in making truncate work
> >> on them.
>
> > I agree with you on that point. How about considering a complete
> > restriction instead?
>
> You already broke the safety seal by enabling allow_system_table_mods.
> Perhaps the documentation of that is not scary enough?
>
> Allows modification of the structure of system tables as well as
> certain other risky actions on system tables. This is otherwise not
> allowed even for superusers. Ill-advised use of this setting can
> cause irretrievable data loss or seriously corrupt the database
> system.
>

I was actually referring to just the truncation part here, not any DML
operations, as I've observed their usage in certain extensions.
However, truncation is just used for pg_largeobject and that too only
during pg_upgrade, so for other catalogs truncation can be avoided.
But that is just my perspective; if it's not essential, we can
possibly stop this discussion here.

Thank you to everyone for sharing your valuable insights.

--
With Regards,
Ashutosh Sharma.