[Bug 1916935] Re: Major changes in sorting method of glibc on Ubuntu 18.04 after upgrading to Ubuntu 18.04.5

[Christian Ehrhardt ]

Hi,
to simplify the following text let us call order that lists 1-1 first "1-1" and the one that lists 11 first "11".

I checked the following:
bionic container (up to date) => 11
focal container (up to date) => 1-1
hirsute container (up to date) => 1-1
bionic vm (up to date) => 11
bionic vm (downgraded all) => 11
bionic vm (downgraded all + re-login) => 1-1

So it seems to be related to something that is applied while logging in
(maybe some more ENV/Locale magic?).

bionic vm (glibc upgraded again) => 1-1
bionic vm (glibc upgraded again + re-login) => 1-1

So it was not glibc (that included libc-bin libc6 locales multiarch-support).
So it was none of these ... ?!?
Let me check if I can 

bionic vm (all-upgraded) => 1-1
bionic vm (all-upgraded + re-login) => 11

Ok so I know the following for now:
1. some upgrade breaks/changes this
2. it is not glibc
3. it needs a re-login to have effect

I did the following experiment.
All downgraded, one session kept up, one session re-logged.
That gave me both behaviors with the same software.


Comparing the ENV and EXPORT of those two I've found:

$ diff 11.env 1-1.env | grep LC
< LC_MEASUREMENT=C.UTF-8
> LC_MEASUREMENT=de_DE.UTF-8
< LC_PAPER=C.UTF-8
< LC_MONETARY=C.UTF-8
> LC_PAPER=de_DE.UTF-8
> LC_MONETARY=de_DE.UTF-8
< LC_NAME=C.UTF-8
> LC_NAME=de_DE.UTF-8
< LC_ADDRESS=C.UTF-8
< LC_NUMERIC=C.UTF-8
> LC_ADDRESS=de_DE.UTF-8
> LC_NUMERIC=de_DE.UTF-8
< LC_TELEPHONE=C.UTF-8
> LC_TELEPHONE=de_DE.UTF-8
< LC_IDENTIFICATION=C.UTF-8
> LC_IDENTIFICATION=de_DE.UTF-8
< LC_TIME=C.UTF-8
> LC_TIME=de_DE.UTF-8

Seeing that one of them carried my local LC info also indicates that the
problem might only affect "some" systems depending on their local
language settings.

In my case it came down to
LC_NUMERIC=de_DE.UTF-8
vs
LC_NUMERIC=C.UTF-8

That made it behave constantly the same.
No a question might be which upgrade changed that ... ?

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https://bugs.launchpad.net/bugs/1916935

Title:
  Major changes in sorting method upgrade 18.04->18.04.5 due to base-
  files change

Status in base-files package in Ubuntu:
  New
Status in glibc package in Ubuntu:
  Invalid
Status in postgresql-10 package in Ubuntu:
  Invalid
Status in base-files source package in Bionic:
  New

Bug description:
  I had an Ubuntu 18.04.0 with Postgres 9.6.

  Before Ubuntu upgrade following command result was:

  [code]
  vodka at ubuntu140:~$  ( echo "1-1"; echo "11" ) | LC_COLLATE=en_US.UTF-8 sort
  1-1
  11
  [/code]

  But after upgrading Ubuntu 18.04 to latest release via apt upgrade
  (18.04.5) result of the command above totally changed:

  [code]
  vodka at ubuntu140:~$ ( echo "1-1"; echo "11" ) | LC_COLLATE=en_US.UTF-8 sort
  11
  1-1
  [/code]

  Due to this our production Postgres database started work very slowly
  and we had a long downtime for REINDEX. Sorting method is very
  important for Postgres database:
  https://wiki.postgresql.org/wiki/Locale_data_changes

  Please, read "Testing collation" part.

  Is it normal behavior for Ubuntu? Why glibc totally changed within LTS
  release without 'major upgrade'? I did not expect this...

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: libc-bin 2.27-3ubuntu1.4
  ProcVersionSignature: Ubuntu 4.15.0-136.140-generic 4.15.18
  Uname: Linux 4.15.0-136-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.23
  Architecture: amd64
  Date: Thu Feb 25 13:13:03 2021
  Dependencies:
   gcc-8-base 8.4.0-1ubuntu1~18.04
   libc6 2.27-3ubuntu1.4
   libgcc1 1:8.4.0-1ubuntu1~18.04
  InstallationDate: Installed on 2021-02-25 (0 days ago)
  InstallationMedia: Ubuntu-Server 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  SourcePackage: glibc
  UpgradeStatus: No upgrade log present (probably fresh install)

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