Horton

Re: Collation versioning

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Christoph Berg <myon@debian.org>, Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2018-09-05T15:20:19Z
Lists: pgsql-hackers 
On Wed, Sep 5, 2018 at 3:35 AM Christoph Berg <myon@debian.org> wrote:
> Re: Thomas Munro 2018-09-04 <CAEepm=0uEQCpfq_+LYFBdArCe4Ot98t1aR4eYiYTe=yavQygiQ@mail.gmail.com>
> > I was reminded about that by recent news
> > about an upcoming glibc/CLDR resync that is likely to affect
> > PostgreSQL users (though, I guess, probably only when they do a major
> > OS upgrade).
>
> Or replicating/restoring a database to a newer host.

Yeah.

> > Does anyone know
> > of a way to extract a version string from glibc using existing
> > interfaces?  I heard there was an undocumented way but I haven't been
> > able to find it -- probably because I was, erm, looking in the
> > documentation.
>
> That sounds more robust. Googling around:
>
> https://www.linuxquestions.org/questions/linux-software-2/how-to-check-glibc-version-263103/
>
> #include <stdio.h>
> #include <gnu/libc-version.h>
> int main (void) { puts (gnu_get_libc_version ()); return 0; }
>
> $ ./a.out
> 2.27
>
> Hopefully that version info is fine-grained enough.

Hmm.  I was looking for locale data version, not libc.so itself.  I
realise they come ultimately from the same source package, but are the
locale definitions and libc6 guaranteed to be updated at the same
time?  I see that the locales package depends on libc-bin >> 2.27 (no
upper bound), which in turn depends on libc6 >> 2.27, << 2.28.  So
perhaps you can have a system with locales 2.27 and libc6 2.28?  I
also wonder if there are some configurations where they could get out
of sync because of manual use of locale-gen or something like that.
Clearly most systems would have them in sync through apt-get upgrade
though, so maybe gnu_get_libc_version() would work well in practice?

-- 
Thomas Munro
http://www.enterprisedb.com

Commits

  1. Doc: Document known problem with Windows collation versions.

  2. Add collation versions for FreeBSD.

  3. Tolerate version lookup failure for old style Windows locale names.

  4. Track collation versions for indexes.

  5. Add pg_depend.refobjversion.

  6. Remove pg_collation.collversion.

  7. Fix the MSVC build for versions 2015 and later.

  8. Add collation versions for Windows.

  9. Implement type regcollation

  10. Use libc version as a collation version on glibc systems.

  11. Make type "name" collation-aware.