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
