On Mon, 3 May 2021 at 19:00, Peter Geoghegan <p...@bowt.ie> wrote: > > On Mon, May 3, 2021 at 9:45 AM Robert Haas <robertmh...@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.
For IoT, as far as I know, one of the constraints is that there exists some unique constraint on the table, which also defines the ordering. Assuming that that is the case, we can use <unique key> + <inserting transaction id> to identify tuple versions. With regards, Matthias van de Meent.
