[debian-mysql] tentative release notes item

[Vincent McIntyre]

On Fri, Feb 17, 2017 at 07:05:37PM +0200, Otto Kekäläinen wrote:
> 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.
> 

The release notes value brevity, so let me try this on you:

+    Note that the database binary data file formats are not backwards
+    compatible, so once you have upgraded to MariaDB 10.1 you will
+    not be able to switch back to any previous version of MariaDB or
+    MySQL unless you have a proper database dump. Therefore, before
+    upgrading, please make backups of all important databases with
+    an appropriate tool such as <command>mysqldump</command>.

The second part is not relevant for the stretch release notes
(which assumes people are upgrading from jessie) but will be
important information for stretch+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.
> 

You mean this bit?

+    See the <ulink url="http://wiki.debian.org/Teams/MySQL">Debian MySQL Team
+    wiki page</ulink> and the
+    <ulink url="http://packages.debian.org/msyql-defaults">mysql-default
+    package page</ulink> for more information.

My intention was to provide a path for people wanting to know more
about the situation with MySQL 5.7, so perhaps this is better:

+    See the <ulink url="http://wiki.debian.org/Teams/MySQL">Debian MySQL Team
+    wiki page</ulink> for current information about the mysql-related
+    software availble in Debian.

?

Thank you for your thoughtful comments
Vince

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