Re: [PATCH] hrmib cache for dpkg

[Goswin von Brederlow <goswin-v-b@web.de>]

Anders F Björklund <afb@users.sourceforge.net> writes:

> Hi all,
>
> I made a quick port of the "HR-MIB cache" for net-snmp of rpm,
> so that it can be used with the dpkg packaging system as well.
>
> What it does is that it keeps a simple directory of files in
> /var/cache/hrmib with one entry for each package, that has a
> timestamp of when the package was installed. So this directory
> can be used to get a package list, without needing db or grep.
>
> This is different from a normal cache dumped from cron or so,
> in that the package manager itself keeps it up-to-date at all
> times by adding and removing files as packages are modified.
> The initial cache can easilly be populated by e.g. touch(1).
>
>
> The files are named in a simple N-V-R.A style, without epochs.
> And for rpm, those "gpg-pubkey" packages aren't listed either.
>
> That is, the file list of the hrmib cache directory should be
> the same as the output of one of the following shell scriptlets:
>
> rpm -qa --queryformat="%{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}\n" |
> grep -v ^gpg-pubkey- # remove public keys
>
> dpkg-query -W --showformat='${Package}-${Version}.${Architecture}\n' |
> sed -e 's/[0-9]\{1,\}://' # remove epochs
>
> The cache must first be populated with the currently installed
> packages, the code only makes sure that it is kept up-to-date.
>
> To get the installation date of each package, one can loop over
> the installed package names and touch the files with a date of:
>
> rpm -q --queryformat="%{INSTALLTIME:date}" $package
>
> ls -l --time-style="+%a %b %e %H:%M:%S %Y" /var/lib/dpkg/info/
> $package.list | cut -d\  -f6-10
>
>
> Attaching patch from the git repository, tried with a similar
> version for the dpkg 1.14 version present in Ubuntu 9.04...
>
> It is available in rpm since version 4.4.7, by uncommenting
> the %_hrmib_path macro in the /usr/lib/rpm/macros config...
>
> --anders
>
>
> PS. It can also be used for doing bash-completion of packages.
>     There are patches for this available elsewhere on the net.

A few points:

1) If the $package.list file already contains all that information for
the current packages in its timestamp then what exactly is the use of
this? Seems more like a log than a cache.

2) If versions are taken without epochs then versions can collide and
they won't work well.

3) Each new version creates a new file. Who cleans up obsolete files?
Or is the "cache" supposed to grow and grow and grow?

4) /var/log/dpkg seems to also alraedy have the info.

MfG
        Goswin