link that explain ICU_LOCALE locale concept about local variant code and keywords.

code from
https://www.postgresql.org/message-id/flat/5e756dd6-0e91-d778-96fd-b1bcb06c161a%402ndquadrant.com

> DROP DATABASE IF EXISTS dbicu;
> CREATE DATABASE dbicu LOCALE_PROVIDER icu LOCALE 'en_US' ICU_LOCALE
> 'en-u-kf-upper' template 'template0';
> \c dbicu
> CREATE COLLATION upperfirst (provider = icu, locale = 'en-u-kf-upper');
> CREATE TABLE icu(def text, en text COLLATE "en_US", upfirst text COLLATE
> upperfirst);
> INSERT INTO icu VALUES ('a', 'a', 'a'), ('b','b','b'), ('A','A','A'),
> ('B','B','B');
> SELECT def AS def FROM icu ORDER BY def;
> SELECT def AS en FROM icu ORDER BY en;
> SELECT def AS upfirst FROM icu ORDER BY upfirst;
> SELECT def AS upfirst_explicit FROM icu ORDER BY en COLLATE upperfirst;
> SELECT def AS en_x_explicit FROM icu ORDER BY def COLLATE "en-x-icu";
>
- trying to replicate the above quoted command.
- So I don't know * ICU_LOCALE 'en-u-kf-upper' *the *u *and the *kf *refer
to?
Even I followed
https://unicode-org.github.io/icu/userguide/locale/#the-locale-concept

1. Language code
2. Script code
3. Country code
4. Variant code
5. Keywords

So which website can I get the info about the "kf" and "u".

--
I recommend David Deutsch's <<The Beginning of Infinity>>

Jian