Horton

Re: Collations and Replication; Next Steps

Peter Geoghegan <pg@heroku.com>

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From: Peter Geoghegan <pg@heroku.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Matthew Kelly <mkelly@tripadvisor.com>, Martijn van Oosterhout <kleptog@svana.org>, Peter Eisentraut <peter_e@gmx.net>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Matthew Spilich <mspilich@tripadvisor.com>
Date: 2014-09-17T17:55:55Z
Lists: pgsql-hackers 
On Wed, Sep 17, 2014 at 6:17 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> What I find astonishing is that whoever maintains glibc (or the Red
> Hat packaging for it) thinks it's OK to change the collation order in
> a minor release.  I'd understand changing it between, say, RHEL 6 and
> RHEL 7.  But the idea that minor release, supposedly safe updates
> think they can whack this around without breaking applications really
> kind of blows my mind.

Why wouldn't they feel entitled to? To quote UTS #10 [1]:

"""
Collation order is not fixed.

Over time, collation order will vary: there may be fixes needed as
more information becomes available about languages; there may be new
government or industry standards for the language that require
changes; and finally, new characters added to the Unicode Standard
will interleave with the previously-defined ones. This means that
collations must be carefully versioned.
"""

Indeed, they do version collations with LC_IDENTIFICATION. We just
don't make any attempt to use the version information. In short, this
is our fault.   :-(

[1] http://www.unicode.org/reports/tr10/#Stability
-- 
Peter Geoghegan