[CentOS] Re: Why is yum not liked by some? -- CVS analogy (and why you're not getting it)

Bryan J. Smith b.j.smith at ieee.org
Fri Sep 9 19:58:26 UTC 2005

Les Mikesell <lesmikesell at gmail.com> wrote:
> I've never said I wanted deltas.

Okay, let's scratch RPM deltas then.  That was someone else.

But you _still_ need at least a "delta" on the meta-data.
Whether you delta the meta-data files, or you keep multiple
copies, you _must_ do so.

YUM repositories do _not_ keep a running journal of changes
in their meta-data.  And YUM clients _only_ access that
meta-data.  YUM clients do _not_ inspect the RPM tree for
resolution, only the meta-data.

My "conceptual hack" is a way to maintain multiple copies of
the repo's meta-data, so you can look up older versions of
the repository.  It's not as good as a delta of the
repository, and you "can't regenerate an old repository," but
it does let you reference previous meta-data sets that were
previously generated.

Which does most of what you want.  You want to be able to
pass a date that worked on another system, to any subsequent
system.  So you can access the repository's meta-data from
that time by passing date.  But, _again_, that requires the
maintainance of _multiple_ sets of the repo meta-data.

The repo meta-data, which is what the YUM client uses, does
_not_ contain a history -- only the current set of files, and
there is no "date" information (nor can there be without

> I've said I wanted yum to not consider additions to a 
> repository past a certain timestamp so it will make the
> same update decision it did a week or so ago even if the
> repostitory has additions.

And I said that is _impossible_!

The YUM client _never_ accesses date information during

The YUM repository is a "static web site" and cannot provide
that information.

The YUM repository contains meta-data matched the
_discrete_date_ that "createrepo" or whatever tool that
created the meta-data list.

And that's what the YUM client accesses.

To add in date information and all the meta-data associated
would massively bloat the meta-data files.  Which is why I
suggested that conceptual hack, to serve up the meta-data
from specific times in the past.

Do you understand this now?

Bryan J. Smith                | Sent from Yahoo Mail
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