Development -> Release use of --oldpackage

[seth vidal]

On Sun, 2006-09-03 at 10:35 +0100, Andy Green wrote:
> On a related issue, I learned last week about rpmcache and what was 
> apparently the old style of repo content distribution based around 
> detached RPM headers into a separate RPM database.  Can anyone gifted 
> with the Redhat/Fedora instrutional memory of the time (Seth?) summarize 
> what drove the migration to a completely separate XML metadata database 
> system?  The old way sounds more economic with data and code from what I 
> understand of it.
> 

1. there was no concept of old-style repositories - that's just
revisionist history

2. there was no concept of multiple repositories with rpm -aid and
rpmcache. Apt and yum were the first two tools to give multiple
repository support for rpm-based systems.

3. while rpm -aid/rpmcache _might_ have worked for depresolution (we
have almost zero evidence of it working in anything, let alone on a
large scale) for doing any sort of other querying it was much, much
heavier.

4. Trundling around the full rpm header blob is much heavier than just
the important metadata. This is why we moved away from compressed
headers from yum 1.X and 2.0 days into the xml metadata.

5. the depresolution mechanism was just not as flexible or easily
corrected as the ones written in other tools. While the rpm-developers
kept threatening to write a depresolver to "put us all out of
business" (yes, actual quote) it never materialized. So, rather than
wait for something to happen that we had no reason to believe would and
rely on a structure we didn't have much influence over we decided to do
something ourselves.

xml was chosen b/c:
  1. didn't have to play games with which language good parse it
  2. you could check it for consistency
  3. you could extend it and and add revisions that could be counted on
  4. originally, we had worked on the xml-metadata to include package
information for solaris and deb packages. Not just rpms. You'll notice
there is a format-specific tag section in the xml-metadata for that
reason.

-sv