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Re: dbconfig-common: near future change in dependency stack

Excerpts from The Wanderer's message of 2016-01-30 04:28:42 -0800:
> On 2016-01-30 at 04:51, Paul Gevers wrote:
> > Hi Frederic-Emmanuel,
> > 
> > On 30-01-16 09:30, PICCA Frederic-Emmanuel wrote:
> >> Do you know if dbconfig-common will integrate a way to switch from
> >> mysql to mariadb in the near futur. something whcih can help do the
> >> migration database from mysql to mariadb.
> > 
> > Actually, I don't think that is in scope of dbconfig-common. I would
> > rather expect that MariaDB would provide that functionality. It is
> > required for more packages and situations than just those supported
> > by dbconfig-common.
> Are there even cases where this is necessary?
> Within the last year, I encountered an unacceptable - but intentional -
> change in the MySQL client interface, so I removed the MySQL packages
> and installed the MariaDB ones.

Which client interface would that be? libmysqlclient18 is still provided
by mysql, even if you install MariaDB.

> My existing database was picked up and used without issues; the
> transition was, on that level, pretty much seamless as far as I recall.
> I might have needed to re-apply some configuration tweaks in different
> config files, but nothing more than that.

This is a one-way trip as of MariaDB 10. MariaDB 5.5 was compatible with
MySQL 5.5 and allowed using the same on-disk files. But MySQL may not
know how to read all of the files produced by MariaDB 10+. So I would
not count on this working again in the future. They're truly forks, and
you will need to backup/restore to make this work.

> This seems to imply that either migration is not required, or MariaDB
> already performs the needed migration transparently. (Or else that I'm
> forgetting some part of the transition process, which is not
> impossible.)
> I can imagine that there could be cases where migration would be
> required, but I'm not aware of any, and it didn't even occur to me to
> expect that I might need to do any in my own case. I expected that the
> two would be seamlessly compatible on the database level, and that
> expectation seems to have been borne out.

Yeah, that would be nice, but the reality is, code is only flowing
_away_ from MySQL at this point. MariaDB's changes don't go back into
MySQL. So the forks will just get further and further apart.

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