On 10 Feb 2017 23:05, "Justin Cappos" <[email protected]> wrote:

I think the difference Sebastien is trying to say is that you need info
from *all* pieces of static metadata.  Not just that from the packages you
will end up installing.

Backtracking dependency resolution will be much more like the wheel model.
If one does not backtrack (which is true most of the time), it only needs
the metadata from the things you end up install.


This is key for PyPI I think - for the yum -> dnf transition, one of the
biggest still unsolved problems is the increase in the amount of metadata
that needs to be transferred (although the file lists used for
install-by-filename are a big contributing factor to that).

You can fairly readily see this in Docker container builds that rely on dnf
- even on a fast connection, you may spend more than a minute downloading
dependency metadata.

It would take a *lot* of server round trips for per-package metadata
retrieval  to start comparing to bulk download times for the metadata for
90k+ packages.

Cheers,
Nick.
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