Re: Collation version tracking for macOS

On Sun, Jun 12, 2022 at 11:59 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
>
> On Sat, Jun 11, 2022 at 4:21 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> > What about "time travel collations", but without the time travel part?
> > That is, what about supporting multiple ICU versions per cluster, but
> > not per database? So you could upgrade the OS and Postgres, using
> > standard packages that typically just use the latest ICU version --
> > typically, but not always. If you happen to have been on an older
> > version of ICU on upgrade, then that version of ICU will still work at
> > the level of a whole database -- your database. Maybe you can create
> > new databases with old and new ICU versions if you want to.
> >
> > That obviously runs into the problem of needing to eventually do a
> > dump and reload -- but I suppose that "eventually" could be a very
> > long time. At least the OS package doesn't declare one version of ICU
> > the blessed version, now and forever, effectively vendoring ICU in a
> > backdoor fashion. At least old databases have significant runway,
> > while at the same time new databases that want to use the same
> > standard Postgres package aren't forced to use the same ancient ICU
> > version.
>
> Hmm. I think that's effectively what you'd get using my "distinct
> collation" patch (v1, or this much better v3, attached), if you put
> version prefixes in colliculocale, and updated them in the template
> database after an OS upgrade to affect new databases. I realise you
> probably mean something a little more automatic...

Thinking some more about what you said above: really, most people only
care about the default collation. I'm not yet sure what I think
initdb should put into pg_collation when importing the initial set of
collation objects in the "distinct" world (perhaps an un-prefixed and
a prefixed variant of each, with names ending -x-icu and -x-icu63?),
but as for the default collation, I should point out that the
"distinct" patch already gives you a nailed-to-the-ground database
approximately as you described above if you just do something like
this:

postgres=# create database db2 locale_provider = icu icu_locale =
'67:en' template = template0 ...;

Small bugfix attached (v3 was accidentally calling uiter_setUTF8() and
u_errorName() directly in a couple of places).