Re: [HACKERS] Can ICU be used for a database's default sort order?

Hi everyone!

> 10 февр. 2018 г., в 20:45, Andrey Borodin <x4mmm@yandex-team.ru> написал(а):
>
> I'm planning to provide review
>

So, I was looking into the patch.
The patch adds:
1. Ability to specify collation provider (with version) in --locale for initdb and createdb.
2. Changes to locale checks
3. Sets ICU as default collation provider. For example "ru_RU@icu.153.80.32.1" is default on my machine with patch
4. Tests and necessary changes to documentation

With patch I get correct ICU ordering by default
postgres=# select unnest(array['е','ё','ж']) order by 1;
 unnest
--------
 е
 ё
 ж
(3 rows)

While libc locale provides incorrect order (I also get same ordering by default without patch)

postgres=# select c from unnest(array['е','ё','ж']) c order by c collate "ru_RU";
 c
---
 е
 ж
 ё
(3 rows)


Unfortunately, neither "ru_RU@icu.153.80.32.1" (exposed by LC_COLLATE and other places) nor "ru_RU@icu" cannot be used
bycollate SQL clause. 
Also, patch removes compatibility with MSVC 1800 (Visual Studio 2013) on Windows XP and Windows Server 2003. This is
doneto use newer locale-related functions in VS2013 build. 

If the database was initialized with default locale without this patch, one cannot connect to it anymore
psql: FATAL:  could not find out the collation provider for datcollate "ru_RU.UTF-8" of database "postgres"
This problem is mentioned in commit message of the patch. I think that this problem should be addressed somehow.
What do you think?

Overall patch looks solid and thoughtful work and adds important functionality.

Best regards, Andrey Borodin.