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From: "Daniel Verite" <daniel@manitou-mail.org>
Subject: Re: Collation version tracking for macOS
To: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: Thomas Munro <thomas.munro@gmail.com>,
 Rod Taylor
 <rbt@rbt.ca>,
 Jim Nasby <nasbyj@amazon.com>,
 Jeremy Schneider
 <schneider@ardentperf.com>,
 Peter Eisentraut
 <peter.eisentraut@enterprisedb.com>,
 Pgsql-Hackers <pgsql-hackers@postgresql.org>
In-Reply-To: <1310017.1654631012@sss.pgh.pa.us>
Date: Wed, 08 Jun 2022 21:40:43 +0200
Message-Id: <6b0bc332-ed6d-4848-a128-4dd63d1160a1@manitou-mail.org>
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	Tom Lane wrote:

> Yeah, and it's exactly at the level of quirks that things are likely
> to change.  Nobody's going to suddenly start sorting B before A.
> They might, say, change their minds about where the digram "cz"
> sorts relative to single letters, in languages where special rules
> for that are a thing.

Independently of these rules, all Unicode collations change frequently
because each release of Unicode adds new characters. Any string
that contains a code point that was previously unassigned is going
to be sorted differently by all collations when that code point gets
assigned to a character.
Therefore the versions of all collations need to be bumped at every
Unicode release. This is what ICU does.

If the libc in macOS doesn't follow Unicode, that's not relevant
to macOS, but let's assume an OS that tries to be up-to-date.
If major OS upgrades happen every year or less frequently,
each OS upgrade is likely to imply an upgrade of all the collations,
since the interval between Unicode releases tends to be a year
or less:
https://www.unicode.org/history/publicationdates.html


Best regards,
--=20
Daniel V=E9rit=E9
https://postgresql.verite.pro/
Twitter: @DanielVerite