Re: pgsql: Allow tailoring of ICU locales with custom rules

On Wed, 2023-03-08 at 16:03 +0000, Peter Eisentraut wrote:
> Allow tailoring of ICU locales with custom rules

Late review:

* Should throw error when provider != icu and rules != NULL

* Explain what the example means. By itself, users might get confused
wondering why someone would want to do that.

* Also consider a more practical example?

* It appears rules IS NULL behaves differently from rules=''. Is that
desired? For instance:
  create collation c1(provider=icu,
    locale='und-u-ka-shifted-ks-level1',
    deterministic=false);
  create collation c2(provider=icu,
    locale='und-u-ka-shifted-ks-level1',
    rules='',
    deterministic=false);
  select 'a b' collate c1 = 'ab' collate c1; -- true
  select 'a b' collate c2 = 'ab' collate c2; -- false

* Can you document the interaction between locale keywords
("@colStrength=primary") and a rule like '[strength 2]'?

Regards,
    Jeff Davis