Re: [18] Policy on IMMUTABLE functions and Unicode updates

On Mon, Jul 22, 2024 at 09:34:42AM -0700, Jeff Davis wrote:
> On Mon, 2024-07-22 at 11:14 -0400, Robert Haas wrote:
> > On Mon, Jul 22, 2024 at 10:26 AM Peter Eisentraut <peter(at)eisentraut(dot)org> wrote:
> > > I disagree with that.  We should put ourselves into the position to
> > > adopt new Unicode versions without fear.  Similar to updates to
> > > time
> > > zones, snowball, etc.
> > >
> > > We can't be discussing the merits of the Unicode update every year.
> > > That would be madness.
> >
> > Yeah, I agree with that 100%.
>
> It's hard for me to argue; that was my reasoning during development.
>
> But Noah seems to have a very strong opinion on this matter:
>
> https://www.postgresql.org/message-id/20240629220857.fb.nmisch%40google.com
>
> and I thought this thread would be a better opportunity for him to
> express it. Noah?

Long-term, we should handle this like Oracle, SQL Server, and DB2 do:
https://postgr.es/m/CA+fnDAbmn2d5tzZsj-4wmD0jApHTsg_zGWUpteb=OMSsX5rdAg@mail.gmail.com

Short-term, we should remedy the step backward that pg_c_utf8 has taken:
https://postgr.es/m/20240718233908.52.nmisch@google.com
https://postgr.es/m/486d71991a3f80ec1c47e1bd7931e2ef3627b6b3.camel@cybertec.at

$SUBJECT has proposed remedy "take more care with Unicode updates". If one
wanted to pursue that, it should get more specific, by giving one or both of:

(a) principles for deciding whether a Unicode update is okay
(b) examples of past Unicode release changes and whether PostgreSQL should
adopt a future Unicode version making a similar change

That said, I'm not aware of an (a) or (b) likely to create an attractive
compromise between the "index scan agrees with seqscan after pg_upgrade" goal
(https://postgr.es/m/20240706195129.fd@rfd.leadboat.com) and the "don't freeze
Unicode data" goal
(https://postgr.es/m/CA+TgmoZRpOFVmQWKEXHdcKj9AFLbXT5ouwtXa58J=3ydLP00ZQ@mail.gmail.com)
The "long-term" above would satisfy both goals. If it were me, I would
abandon the "more care" proposal.