Re: Re: CREATE COLLATION does not sanitize ICU's BCP 47 language tags. Should it?

Noah Misch <noah(at)leadboat(dot)com> writes:
> On Mon, Sep 25, 2017 at 09:36:44AM -0700, Peter Geoghegan wrote:
>>> I think it's inevitable that a certain number of users are going to
>>> have to cope with ICU version changes breaking stuff.

>> Wasn't the main point of adopting ICU that that doesn't happen when it
>> isn't essential?

> I wouldn't describe it that way. I agree that few, if any, ICU upgrades will
> remove country or language codes. Overall, though, almost every ICU upgrade
> will be difficult. Each ICU release, even a minor release like 58.2, changes
> the sorting rules in some tiny way. You then see "Rebuild all objects
> affected by this collation" messages.

Sure, but dealing with that is mechanical: reindex the necessary indexes
and you're done. I think it's important to distinguish that from a case
where users have to change their collation definitions. That is a
qualitatively different, and much harder, upgrade problem.

I'd also argue that the point of adopting ICU was exactly so we *could*
distinguish those cases, and limit the scope of a normal upgrade to
"reindex these identifiable indexes and you're done". In the libc world,
when you upgrade libc's locale definitions, you have no idea what the
consequences are.

regards, tom lane