delta repo data - FTL

[Tomas Mlcoch]

Hi poma,

the short answer is no.

The idea (to have deltas between two repodata) and purpose (be able to gen and apply such deltas) is the same, but the used techniques and ideas are different.

Few notes about design could be found on wiki of the project [1].

In few bullets:

* My deltarepo works with deltas which are itself valid repositories.
* The delas are based on XML files (not the sqlite)
* The sqlite databases are of course supported but they are generated from the XML files.
* My deltarepo introduces concept of contenthash [2]
** Because the repodata can be generated by different tools (the XML files can have different formatting), the order of packages can be different, etc.
** The contenthash should quiet uniquely identify "the content" of the repository (its packages).
* There are no "keyframes" - each version of repo has its unique contenthash
* There should be bunch of deltas between different repo versions
* The updater uses the Dijkstra's algorithm to find the best path (if available) between two repo versions.
** Updater also checks if the cost of the usage of deltas is not higher then downloading of new repodata directly.
** The choice if download a whole repo or just deltas is up to client (if there is a path (ordered sequence of deltarepos) from the client's version of repo to the most current version of the repo and the cost of this path (total size) is less then the cost of the complete repo - then the updater should use prefer the deltas).

>From the repo administrator point of view:
* There is one complete repo (the most current one)
* There are a lot of different deltas between different versions of the repo

I hope that this short summary is understandable :)


Regards
Tomas

[1] https://github.com/Tojaj/DeltaRepo/wiki/DeltaRepo-Design
[2] https://github.com/Tojaj/DeltaRepo/wiki/DeltaRepo-Design#contenthash-of-a-repo


----- Original Message -----
> 
> This is what I wanted to ask, and then I found a post from Seth,
> http://lists.baseurl.org/pipermail/yum-devel/2011-March/008047.html
> "delta repodata"
> 
> "Passing along this longer version of Martin's idea for providing deltas
> of repodata for yum.
> 
> this idea came up at fudcon in AZ and I think it may be a great goal for
> F16 or beyond.
> 
> Anyone have any thoughts on this?"
> 
> And by the way I came across Tomas's project,
> https://github.com/Tojaj/DeltaRepo
> 
> DeltaRepo - Set of tools that generate/merges differences between an old and
> a new version of a repodata.
> 
> Tomas, is this what Set wrote and your DeltaRepo project in any way
> connected?
> 
> 
> poma