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

[Balint Reczey]

Thank you for the bug report.
I' could not reproduce the old behaviour just by downgrading glibc, but will check it with an original 18.04.0 installation, then upgrading it.

I'm marking postgresql as affected, for better visibility.

** Tags added: rls-bb-incoming

** Also affects: postgresql-10 (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: glibc (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Also affects: postgresql-10 (Ubuntu Bionic)
   Importance: Undecided
       Status: New

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

Title:
  Major changes in sorting method of glibc on Ubuntu 18.04 after
  upgrading to Ubuntu 18.04.5

Status in glibc package in Ubuntu:
  New
Status in postgresql-10 package in Ubuntu:
  Incomplete
Status in glibc source package in Bionic:
  New
Status in postgresql-10 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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