A more efficient up2date service using binary diffs

[M A Young]

On Fri, 11 Mar 2005, Jeff Johnson wrote:

> This patch
>     https://svn.uhulinux.hu/packages/dev/zlib/patches/02-rsync.patch
> is in rpm-4.4.1 and on by default.
>
> If the payloads in FC4 are not rsyncable right now, then it's because
> beehive is using an
> older version of rpm ... checking ... yep, current rpm payloads should
> be rsync ready:
>
> $ rpm -q --qf '%{rpmversion}\n' perl
> 4.4.1

It seems the option isn't active for FC3 and its updates (which is what I
had tested) so I have repeated the test with a couple of RPMs from
different rawhide mirrors using xdelta, which uses a similar algorithm to
rsync, and found the following sizes

libgcj-4.0.0-0.31.i386.rpm 13942525
libgcj-4.0.0-0.32.i386.rpm 13950302
xdelta of rpms              6911651
xdelta of header + cpio     3723074

thus there is a significent saving in size for small changes, though you
can do even better with more processing. Also from my experience with
openoffice rpm library rpms don't diff as well as other packages, so the
typical saving might be better than this example.

	Michael Young