On Mon, May 3, 2021 at 9:45 AM Robert Haas <robertmhaas@gmail.com> wrote:
> But if you're saying those identifiers have to be fixed-width and 48
> (or even 64) bits, I disagree that we wish to have such a requirement
> in perpetuity.
Once you require that TID-like identifiers must point to particular
versions (as opposed to particular logical rows), you also virtually
require that the identifiers must always be integer-like (though not
necessarily block-based and not necessarily 6 bytes). You've
practically ensured that clustered index tables (and indirect indexes)
will never be possible by accepting this. Those designs are the only
real reason to have truly variable-length TID-like identifiers IMV (as
opposed to 2 or perhaps even 3 standard TID widths).
You don't accept any of that, though. Fair enough. I predict that
avoiding making a hard choice will make Jeff's work here a lot harder,
though.
--
Peter Geoghegan