Zsync for Packages files

[Max Bowsher]

Paul Sladen wrote:
> On Tue, 21 Jul 2009, Lars Wirzenius wrote:
>> ma, 2009-07-20 kello 22:46 +0200, Tollef Fog Heen kirjoitti:
>>> You'll need to get quite a lot of small files,
>> Surely apt uses a single TCP connection to fetch all the pdiff files?
> 
> The current implemenation is fairly dumb, the loop being roughly:
> 
>   while hash(Packages) != latest_hash:
>       fetch_and_apply_new_pdiff(hash)
> 
> A major optimisation would be to have apt pre-calculate the entire path
> through the available pdiffs.  Calculating a path beforehand would allow
> deciding if a fresh download would be smaller/faster, or if a shorter path
> (via a per-day, or per-week combined patch) would work out better.

Yes.

> However, the concept of contextual diffs for updates is not-great as they
> duplicate not only the data to be applied, but also the data to be removed.

pdiffs are not contextual. They are a very limited form of "ed" scripts,
and hence do not duplicate data.

Max.


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