From: "Regina Obe" <lr@pcorp.us>
To: "'Tom Lane'" <tgl@sss.pgh.pa.us>,
	"'Peter Eisentraut'" <peter.eisentraut@enterprisedb.com>
Cc: "'Sandro Santilli'" <strk@kbt.io>,
	<pgsql-hackers@lists.postgresql.org>,
	"'Jeff Davis'" <pgsql@j-davis.com>
References: <000b01d97465$c34bbd60$49e33820$@pcorp.us> <3353947.1682092131@sss.pgh.pa.us> <ZELDOktA75yYG4Z2@hst.kbt.io> <533d93c5-f604-8e5f-4a48-975c08c53d59@enterprisedb.com> <3365333.1682098091@sss.pgh.pa.us>
In-Reply-To: <3365333.1682098091@sss.pgh.pa.us>
Subject: RE: Order changes in PG16 since ICU introduction
Date: Fri, 21 Apr 2023 13:37:25 -0400
Message-ID: <002d01d97477$f0395640$d0ac02c0$@pcorp.us>
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit
Thread-Index: AQGxk+8S/MfoZUDGLFz42A+I7+xfAAHR8HzHAhsEYz4Bynr6awHasdxCr0k1y5A=
Content-Language: en-us
Archived-At: <https://www.postgresql.org/message-id/002d01d97477%24f0395640%24d0ac02c0%24%40pcorp.us>
Precedence: bulk

> Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
> > If the database is created with locale provider ICU, then lc_collate
> > does not apply here, so the result might be correct (depending on what
> > locale you have set).
> 
> FWIW, an installation created under LANG=C defaults to ICU locale en-US-u-
> va-posix for me (see psql \l), and that still sorts as expected on my
RHEL8 box.
> We've not seen buildfarm problems either.
> 
> I am wondering however whether this doesn't mean that all our carefully
> coded fast paths for C locale just went down the drain.  Does the ICU code
> have any of that?  Has any performance testing been done to see what
impact
> this change had on C-locale installations?  (The current code coverage
report
> for pg_locale.c is not encouraging.)
> 
> 			regards, tom lane

Just  another metric.

On my mingw64 setup, I built a test database on PG16 (built with icu
support) and PG15 (no icu support)

CREATE DATABASE test TEMPLATE=template0 ENCODING = 'UTF8' LC_COLLATE = 'C'
LC_CTYPE = 'C';

I think the above is the similar setup we have when testing.

On PG15 

SELECT '+' <  '-' ;  returns true

On PG 16 returns false

For PG 16, to strk's point, you have to do: to get a true
SELECT '+' COLLATE "C" <  '-'  COLLATE "C";


I would expect since I'm initializing my db in collate C they would both
behave the same