One option smart needs to conquer the world

[Jeff Johnson]

On Feb 22, 2006, at 12:14 PM, Zach Garner wrote:

> Alternative Policies for 'smart upgrade' would probably be a good
> thing. For instance, I would really like a policy similar to 'apt
> upgrade' that does not Remove packages. (apt dist-upgrade is used for
> an upgrade that can install and remove packages)
>
> If there was an option that would prevent downgrading, then the
> packager of smart for fedora could choose to enable it by default, if
> they are so concerned. But users could choose what they want.
>
> Honestly, I could understand some concern. One package that we use at
> my company will potentially modify a database schema on an upgrade. We
> haven't implemented logic (which would take quiet a bit of development
> time) that would do the right thing for a downgrade. There's also no
> way that I know for a packager to specify that their package should
> not be downgraded.
>

Modifying a schema upgrade on package upgrade is what is wrong (imho).

Changing a db schema is intrinsically a risky operation, involving
large copies of data that is subject to implicit conditions (like
enough space on disk to make the copy) that cannot be handled
adequately by any package manager.

Factoring the schema change out of packaging into a separate
script operation is wiser for many reasons, not the least of which
is that smart might decide to downgrade that important package someday
and then you're gonna be pissed ;-)

The point is that there will *always* be exceptions that can/should not
be downgraded. That doesn't mean that the exceptions cannot be handled
with a "Don't downgrade this package." policy. The more interesting (and
solvable) problem is how to specify that policy reliably, so that other,
perfectly sensible, downgrades might be attempted.

73 de Jeff