Date: Tue, 7 Jun 2022 17:38:03 -0400
From: Bruce Momjian <bruce@momjian.us>
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>
Subject: Re: Collation version tracking for macOS
Message-ID: <Yp/FO6pHcYZfOtnq@momjian.us>
References: <ce1174ea-1942-37f0-421e-9ccff400dbcb@enterprisedb.com>
 <231072.1654273317@sss.pgh.pa.us>
 <1874de62-6bec-4bc1-1d14-0a2730b125da@ardentperf.com>
 <CA+hUKGLwT9xBSodtmio-NnGXfkrfVs02O6kg1iwBJSt-XMhW4g@mail.gmail.com>
 <366234.1654289888@sss.pgh.pa.us>
 <0867fe37-abbd-77ba-aafc-572074978bb0@amazon.com>
 <976279.1654561524@sss.pgh.pa.us>
 <CAHz80e76vuRGm0D2sDO52Wyua57WLNM2ug44d1Lk4Y5-PUHmKA@mail.gmail.com>
 <CA+hUKGLXWGKn4WZwNr0bmDSdyQa1+njM5_vRfc1CxiDR1WUK9g@mail.gmail.com>
 <1310017.1654631012@sss.pgh.pa.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1310017.1654631012@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/Yp/FO6pHcYZfOtnq%40momjian.us>
Precedence: bulk

On Tue, Jun  7, 2022 at 03:43:32PM -0400, Tom Lane wrote:
> Thomas Munro <thomas.munro@gmail.com> writes:
> > On Wed, Jun 8, 2022 at 3:58 AM Rod Taylor <rbt@rbt.ca> wrote:
> >> Is this more involved than creating a list of all valid Unicode characters (~144 thousand), sorting them, then running crc32 over the sorted order to create the "version" for the library/collation pair? Far from free but few databases use more than a couple different collations.
> 
> > Collation rules have multiple levels and all kinds of quirks, so that
> > won't work.
> 
> 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.
> 
> The idea of fingerprinting a collation's behavior is interesting,
> but I've got doubts about whether we can make a sufficiently thorough
> fingerprint.

Rather than trying to figure out if the collations changed, have we ever
considered checking if index additions and lookups don't match the OS
collation and reporting these errors somehow?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Indecision is a decision.  Inaction is an action.  Mark Batterson