Re: Collation versioning

On Fri, Nov 8, 2019 at 5:40 PM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
> On Fri, 2019-11-08 at 15:04 +1300, Thomas Munro wrote:
> > 3. We don't know if pre-13 indexes are corrupted or not, and we'll
> > record that with a special value just as in proposal #1, except that
> > we could show a different hint for that special version value. It
> > would tell you can you can either REINDEX, or run ALTER INDEX ...
> > DEPENDS ON COLLATION "fr_FR" VERSION '34.0' if you believe the index
> > to have been created with the current collation version on an older
> > release of PostgreSQL that didn't track versions.

> #3 is the best proposal, but there is still the need to run
> ALTER INDEX on all affected indexes to keep PostgreSQL from nagging.
> Perhaps the situation could be improved with a pg_upgrade option
> --i-know-my-indexes-are-fine that causes a result like #2.
> Together with a bold note in the release notes, this may relieve
> the pain.

I suppose another reason to use such a switch would be if there is a
change in the versioning scheme; for example, as of today in master we
are using the glibc version, but a future glibc release might offer an
interface to query the CLDR version it's using, and then a future
release of PostgreSQL might get support for that, so the strings would
change between major version of PostgreSQL but you might want to be
able to tell pg_upgrade that your indexes are good.