Re: does aptitude really need to lock the status database when downloading?
On Fri, Feb 04, 2011 at 09:47:21AM -0200, Fernando Lemos wrote:
> On Fri, Feb 4, 2011 at 6:57 AM, Stanislav Maslovski
> <stanislav.maslovski@gmail.com> wrote:
> [...]
> >> If you want to have that level of control, why don't you just check it
> >> manually? Use --download-only with apt-get (no dpkg locking this way)
> >> and when it's done, use apt-get without it to install the packages after
> >> making sure that there is no dpkg active anymore.
> >
> > This is possible, however, it is an extra busy work for a user. In any
> > case, I think that holding a lock only for downloading is an overkill
> > and this can be relaxed.
>
> As far as I can tell (and please correct me if I'm wrong), when you
> do, say, an "apt-get upgrade", apt prepares an upgrade "plan" that
> uses a given set of packages. If apt wouldn't lock and parallel to
> that you do an "apt-get install", for example, the original "plan"
> might not be valid anymore (e.g., new "Breaks" or "Conflicts" were
> introduced).
This I understand, as I mentioned in my original mail.
> So a new plan would have to be created, the user would
> have to be asked for confirmation again. Doesn't sound that great.
Actually, it is the opposite. It sounds actually very great
_for_the_target_user_. Because the user who wants this feature will be
aware of what he is doing. For that user the _current_ situation with
the global lock does not seem very great.
Other users will not be affected at all if such a check is indroduced,
because they do not use dpkg when doing an apt-get upgrade.
Unfortunately, I do not know anything about the internal architecture
of apt and friends, therefore I cannot promise any help with it and
may only ask for other people that may be interested in implementing
this. Maybe in a competing software (was there something called cupt?)
> > As Julian Taylor mentioned, there is also another side of the same
> > problem: aptitude itself can be improved so that it is able to
> > download and unpack in parallel. If it were doing this then the lock
> > would be justified.
>
> As far as I know, apt-get already downloads in parallel. Not sure
> about aptitude.
A parallel download is not the same as a download superimposed with
unpacking.
--
Stanislav
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