Solving the compression dilema when rsync-ing Debian versions
It's commonly agreed that compression does prevent rsync from profit of
older versions of packages when synchronizing Debian mirrors. All the
discussion about fixing rsync to solve this, even trough a deb-plugin is
IMHO not the right way. Rsync's task is to synchronize files without
knowing what's inside.
So why not solve the compression problem at the root? Why not try to
change the compression in a way so it does produce a compressed result
with the same (or similar) difference rate as the source?
As my understanding of compression goes, all have a kind of lookup table
at the beginning where all compression codes where declared. Each time
this table is created new, each time slightly different than the
previous one depending on the source. So to get similar results when
compressing means using the same or at least an aquivalent lookup table.
If it would be possible to feed the lookup table of the previous
compressed file to the new compression process, an equal or at least
similar compression could be achieved.
Of course using allways the same lookup table means a deceasing of the
compression rate. If there is an algorithmus which compares the old rate
with an optimal rate, even this could be solved. This means a completly
different compression from time to time. All depends how easy an
aquivalent lookup table could be created without loosing to much of the
compression rate.
O. Wyss
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