RE: [EXTERNAL] Re: Windows Application Issues | PostgreSQL | REF # 48475607

Hi Vishwa,

Could you please help with the questions below?

Thanks!
Haifang

-----Original Message-----
From: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Sent: Monday, May 20, 2024 1:57 PM
To: Haifang Wang (Centific Technologies Inc) <v-haiwang(at)microsoft(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>; Vishwa Deepak <Vishwa(dot)Deepak(at)microsoft(dot)com>; pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: [EXTERNAL] Re: Windows Application Issues | PostgreSQL | REF # 48475607

On Tue, May 21, 2024 at 8:17 AM Haifang Wang (Centific Technologies
Inc) <v-haiwang(at)microsoft(dot)com> wrote:
> What questions do you have? Could you please list them clearly so that Vishwa could help to answer?

I already did, twice, but perhaps Vishwa or others can't see the whole thread, so here is this whole thread in our project email archive:

https://www.postgresql.org/message-id/flat/PH8PR21MB3902F334A3174C54058F792CE5182%40PH8PR21MB3902.namprd21.prod.outlook.com

But let me ask the questions again, with some motivation/reason I want to know in parentheses:

1. What is the oldest Windows release that can understand the "new"
BCP47 locale names, like "tr-TR" or "tr-TR.1452"? (Some PostgreSQL versions, for example PostgreSQL 12, are expected to run on old versions of Windows from long before Windows 10, so we might have to consider this. However, if we go with Tom's idea that we do nothing by default but just allow users to supply their own optional mapping file, then this question becomes unimportant, users can figure out for themselves whether it works, and presumably only 10+ got the update that renamed Turkey to Türkiye. [And in reality, I hope/expect that no one really does run old out-of-support OSes, because that's crazy, but I'm not allowed to assume...])

2. If we translate to BCP47 locale names like "tr-TR" automatically, should we put the ".1452" on the end? What does it mean exactly?
What does it mean if you don't put it there? (I could guess that if you don't put it on, the encoding in "char"-based functions is the "ACP". What I really want to know is, can it be different from the "ACP", and if it is, which functions does it affect? For example if the ACP is 1521 and I call _tolower_l() giving it a locale_t that I opened with "en-US.UTF-8", what happens? I am sure this is a simple question but we are not Windows programmers, you are the first person to show up offering to investigate, and I personally found the docs a bit light on the topic.)

3. Do the new BCP47 locale names give *exactly* the same results for
strcoll() and tolower() etc, as the old "Turkish*" style names? (In other words, is it *exactly the same code and driving data*, just using different labels? Or is it a new locale implementation that could differ arbitrarily in behaviour? If the answer is yes, it's just a new naming scheme, then life will be much much simpler for our users, but if not, then indexes might be corrupted if we tell people to switch to the new BCP47 names, and so we'd better know about that, so we can adjust our advice to users.)