[Rpm-ecosystem] lazy loading of filelists.xml to speed up dnf

Zbigniew Jędrzejewski-Szmek zbyszek at in.waw.pl
Mon Aug 6 16:36:07 UTC 2018

Hi dnf and libsolv developers,

this mail is a continuation of an FPC [1] and a FESCo [2] tickets.

A proposal was made is to disallow packages in Fedora from using file
deps, and to optimize dnf to not load filelists.xml. File deps would
still be supported, because external packages and users want to use
them, but they would not be allowed for distro packages.

Not downloading or loading filelists.xml which are required for file
deps would provide significant bandwidth savings (~47 MB compressed)
and noticeable runtime savings (~10s at dnf startup) in many common

So this is something that is worth exploring, but it's not clear if it
is at all feasible. It seems that dnf would need to support loading
filelists.xml lazily. In the mailing list discussions, some people
said that this would be hard, some people said that it would be
possible… What is the situation here? IIUC, dnf would need to restart
the resolution of a transaction mid-flight once it encounters a file dep,
which would require support across the different layers.
If Fedora commits to making use of this, would it be possible to
implement this in dnf? What kind of changes would be required?

[1] https://pagure.io/packaging-committee/issue/714
[2] https://pagure.io/fesco/issue/1955

Zbyszek, on behalf of FESCo (but not that this writeup is based
on my understanding, so all errors are mine.)

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