[debian-mysql] tentative release notes item

[Otto Kekäläinen]

Hello!

2017-02-17 6:45 GMT+02:00 Vincent McIntyre <vincent.mcintyre at csiro.au>:
> +    Note that once you have switched to MariaDB, it might not possible to
> +    convert your in-place database files back to MySQL automatically, since
> +    Oracle does not maintain tools to convert possible MariaDB features
> +    present in the binary format.

This is true, but this makes it sound very intentional, while it is
actually the same scenario as always - old released cannot read the
binary format of newer releases.

I would suggest to write this instead:

Please make sure you make backups of all important data in productions
systems before you upgrade the database (you should be doing regular
backups anyway). Simply doing a copy of the /var/lib/mysql directory
does not guarantee to produce a consistent database and therefore
using tools like mysqldump or xtradbbackup are recommended. Having a
complete database dump (instead of only the binary data files) is also
the most interoperable data format. Binary data files are not
backwards compatible, so once you have upgraded to MariaDB 10.1, you
will not be able to easily switch back to any previous version of
MariaDB or MySQL unless you have a proper database dump.

And maybe also add:
MariaDB 10.1 cannot read the binary data format of MySQL 5.7. If you
run MySQL 5.7 (not in Debian), you need to upgrade to MariaDB 10.2
(not in Debian) or manually export and import a database dump form
MySQL 5.7 to MariaDB 10.1.


All competent database admins should have backups and test their
upgrade paths before doing it in production, but there are always
those who don't pay attention, so I hope that the part about having
backups is stressed in the release notes.

Not a big deal, but the link to docs could be simply to
https://mariadb.org/ as a general source of info, and let users find
the Knowledge Base and other docs from there then.


- Otto