Re: WARNING! New Perl/Perl-base upgrade removes 141 Sid/Unstable packages
On 2016-09-29 10:17:57 +0100, Darac Marjal wrote:
> Looking at the documentation for SolutionCost, it only makes removals more
> costly. There is no way to say "never remove any packages".
Actually, the problem doesn't seem to be a cost one, but the fact
that Aptitude *skips* solutions where some packages are kept at
their current version (which would allow it to avoid any removal),
i.e. it will never propose such solutions even though they cost
less than the solution proposed first.
> But what if PackageA is something like libc? A hundred packages are to be
> upgraded but PackageB is old and incompatible. Clearly, even though you've
> boosted the cost of removals, it's STILL cheaper to remove PackageB than it
> is to cancel those hundred installs.
Wrong. I've said "removals" in SolutionCost. So, 1 removal is cheaper
than *any* number of canceled actions. If I wanted some compromise
between removals and canceled actions, I would have put something
like: removals + 100 * canceled-actions.
Note than in practice, a single package can block hundreds of upgrades
e.g. during transitions, because there is a temporary failure to
rebuild this package. I generally prefer to wait for a few days than
removing this package. By not proposing such a solution, Aptitude
blocks even upgrades of packages than could be done (unless I upgrade
each other package manually, which is tedious).
--
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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