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Re: A radically different proposal for differential updates




On Tue, Aug 15, 2017 at 09:26:24AM +0200, Christian Seiler wrote:
> Hi there,
> 
> I've come to believe that binary diff packages are not the best way of
> solving this issue. Intead I'd like to propse a radically different
> solution to this issue.
> 
> The gist of it: instead of adding a format for how deltas work, I
> propose to introduce a new format for storing Debian packages that will
> be used for both the initial installation _and_ incremental updates.
> 
> This idea was inspired by the following talk given by Lennart
> Poettering about a new tool he's written (which is already packaged for
> Debian by the way):
> https://www.youtube.com/watch?v=JnNkBJ6pr9s
> 
> 
> 
> Now to my proposal:
> 
> A Debian package currently consists of two files: control.tar.gz and
> data.tar.xz (or .gz). What I want to propose is a new format that does
> not contain a data.tar.xz at all. Instead I'd like to split the
> data.tar.xz into chunks and have the new format only contain an index
> that references these chunks. Let me call this new format "cdeb" for
> "chunked deb".
> 
[...]
> Anyway: thoughts? Regards, Christian

It's of course an awesome idea. But:

I generally agree with the idea of chunk stores. They'd improve
things a lot. Now, instead of chunking the tarfiles, chunk both
the individual files, and the tarfiles. Then, with an index for
the individual files in control.tar listing the chunks, you can
easily reconstruct just the files that changed on your system
and avoid any rebuilding of debs for upgrades :D

That said, I believe that this change won't sell. Replacing the
basic format the repository is made of won't fare well. Too many
tools (most of which probably are not known) rely on the presence
of deb files in archives.

So as sad as it might be, I think we probably have to settle for
delta files.

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