Re: BUG #16577: Segfault on altering a table located in a dropped tablespace

Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> On 2020-Oct-28, Michael Paquier wrote:
>> Haven't thought of that approach, good idea! That would not be
>> backpatchable but that would be a solution that does not require
>> creating files where we don't need them. Did you begin to look at
>> that?

> I haven't started on this one yet, but I intend to do so shortly.

> Strictly speaking, we can still introduce a new category of pg_shdepend
> entries in back branches; it won't break anything that works today.

Yeah, as long as the patched version won't actively fail when those
pg_shdepend entries are missing, I don't think a backpatch is too
hazardous. It might be worth checking that the extra entries don't
create huge problems if one does downgrade after some of them exist
--- but my feeling for how that mechanism works is that it'd Just
Work, and indeed provide the missing DROP protection even without
explicit action by the backend.

I would not be too excited about offering instructions for people
to manually add/remove the dependency entries. The amount of
value added, versus the risks of bollixing things completely,
doesn't sound like a good tradeoff.

regards, tom lane