[debian-mysql] mysql-server-5.5.postrm [was: Re: Resyncing with Ubuntu]

[Clint Byrum]

Excerpts from Robie Basak's message of 2014-02-10 07:24:00 -0800:
> This post is about mysql-server-5.5.postrm.
> 
> Currently, it disables the standard #DEBHELPER# token. I presume this
> causes an issue in Ubuntu with upstart, and so Ubuntu re-enables it
> currently.
> 
> I note that in Debian, the removed token is replaced with
> hand-crafted/copied code of what the token would have caused to be
> included; Ubuntu doesn't remove this, so there is some duplication
> there. I haven't investigated to see if there's a bug here or not.
> 
> As far as I can determine, the reason for this being in Debian is:
> 
> # - Do NOT purge logs or data if another mysql-sever* package is installed (#307473)
> 
> I've looked at that bug, and it seems to be that it is no longer
> relevant in jessie, since other packages no longer exist, and this is
> specifically a mysql-server-5.5 postrm.
> 
> But, we'll have mysql-server-5.6 soon, so we probably want to get this
> right.
> 
> AIUI:
> 
> mysql-server-5.5 owns /var/lib/mysql, and conflicts with
> mysql-server-5.6 (say), which also owns /var/lib/mysql, and they
> conflict. What's the expected behaviour on package purge? Should
> /var/lib/mysql, which contains the relevant database itself, be purged?
> Currently, there's some really ugly code in this area.
> 
> There's a debconf option to say what should happen, but also code to try
> and not do the purge if a different mysql-server-* is installed, since
> otherwise it would destroy the wrong data.
> 
> The whole arrangement seems wrong to me, but I'm not sure of the correct
> solution.
> 
> Can this be fixed by restoring the #DEBHELPER# token, and dropping the
> custom code? I don't see any bug that would be caused by this. But this
> is a tricky area and I'm not entirely sure. In the meantime, the
> existing code seems quite ugly and difficult to maintain, and blocks me
> from adding upstart support cleanly both in Debian and in Ubuntu.

Seems to me that Conflicts is wrong and trying to work around having
to remove mysql-server-5.1 before installing mysql-server-5.5 is no
longer a problem we'll have if we ship a mysql-server-5.6 that simply
Breaks/Replaces mysql-server-5.5.  In this case mysql will be stopped,
5.6 will be configured, and then 5.5 will be removed.

So yes, we need to make it work with the #DEBHELPER# token. I'm certain
this is just neglect, not some clever thing where the MySQL maintainers
found a better solution than "all of the debhelper developers".