[pacman-dev] Thoughts on database initialization and loading process

Dan McGee dpmcgee at gmail.com
Sat Apr 16 19:40:31 EDT 2011

Hey guys,

Hopefully someone has some insight, but I fear that this involves some
pretty intimate knowledge with the alpm dirty internals.

I implemented the local DB "version" check as something on the
transaction process, due to the fact that we call get_pkgcache or
find_package and all those fun methods all over the place with the
expectation that they normally won't fail in any way. This was a bit
of a hack, and has become more apparent as I look at some of the GPG

Due to the lazy loading of the package cache for databases, we never
really know when a database may be initialized, or which call site
will do so. This makes it hard for us to 1) do the local DB sanity
check ASAP and in the right place, and 2) implement signature checking
on databases each time it is accessed, which seems like the prudent
decision to me.

That leaves us with a few options:
1) Don't check database signatures every time, only when we "need to",
e.g. right after download. Not a fan of this one.
2) Only check database signatures if we go through the transaction
layer- just like we do now with the local version check.
3) Add some explicit alpm_dbs_set_in_stone() method that needs to be
called before databases can be used, but after they are registered,
that takes care of some bookkeeping stuff like this. Stinks because it
introduces a rather kludgy API that depends on methods being called in
procedural order (not to mention all frontends will need
modification), but by far the easiest way to resolve this.
4) Fix callsites everywhere that may force a load of the pkgcache to
actually check error return values for the "local db too old" and "gpg
sig check failed" cases, among other, rather than just assuming the
pkgcache is NULL without looking at pm_errno. Best solution as it
requires no API change, but will definitely have a large LOC impact.



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