Re: making relfilenodes 56 bits

On Fri, Aug 26, 2022 at 7:01 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> While working on this solution I noticed one issue. Basically, the
> problem is that during binary upgrade when we try to rewrite a heap we
> would expect that “binary_upgrade_next_heap_pg_class_oid” and
> “binary_upgrade_next_heap_pg_class_relfilenumber” are already set for
> creating a new heap. But we are not preserving anything so we don't
> have those values. One option to this problem is that we can first
> start the postmaster in non-binary upgrade mode perform all conflict
> checking and rewrite and stop the postmaster. Then start postmaster
> again and perform the restore as we are doing now. Although we will
> have to start/stop the postmaster one extra time we have a solution.

Yeah, that seems OK. Or we could add a new function, like
binary_upgrade_allow_relation_oid_and_relfilenode_assignment(bool).
Not sure which way is better.

> But while thinking about this I started to think that since now we are
> completely decoupling the concept of Oid and relfilenumber then
> logically during REWRITE we should only be allocating new
> relfilenumber but we don’t really need to allocate the Oid at all.
> Yeah, we can do that if inside make_new_heap() if we pass the
> OIDOldHeap to heap_create_with_catalog(), then it will just create new
> storage(relfilenumber) but not a new Oid. But the problem is that the
> ATRewriteTable() and finish_heap_swap() functions are completely based
> on the relation cache. So now if we only create a new relfilenumber
> but not a new Oid then we will have to change this infrastructure to
> copy at smgr level.

I think it would be a good idea to continue preserving the OIDs. If
nothing else, it makes debugging way easier, but also, there might be
user-defined regclass columns or something. Note the comments in
check_for_reg_data_type_usage().

--
Robert Haas
EDB: http://www.enterprisedb.com