Re: Evaluation (Re: Proposal: A new approach to differential debs)
- Date: Tue, 22 Aug 2017 22:53:47 +0200
- From: Sebastian Andrzej Siewior <sebastian@xxxxxxxxxxxxx>
- Subject: Re: Evaluation (Re: Proposal: A new approach to differential debs)
On 2017-08-16 00:21:09 [+0200], Julian Andres Klode wrote:
> libreoffice-core (size only):
> -rw-r--r-- 1 jak jak 29M Jul 22 20:02 libreoffice-core_5.3.5~rc1-3_amd64.deb
> -rw-r--r-- 1 jak jak 31M Jul 16 00:10 libreoffice-core_5.4.0~rc2-1_amd64.deb
> -rw-r--r-- 1 jak jak 31M Jul 28 18:29 libreoffice-core_5.4.0-1_amd64.deb
> -rw-r--r-- 1 jak jak 18M Aug 15 23:44 libreoffice-core_5.3.5~rc1-3_5.4.0-1_amd64.pdeb
> -rw-r--r-- 1 jak jak 4.5M Aug 15 23:42 libreoffice-core_5.4.0~rc2-1_5.4.0-1_amd64.pdeb
> For 5.4~rc2 to 5.4 it made a huge difference, for 5.3.5~rc1 to 5.4 not so much,
> so it probably is a good fit for stable updates, but not for unstable and testing.
I would say it depends on the software. Some differs more than other.
> firefox (size & performance):
> -rw-r--r-- 1 jak jak 2.3M Aug 15 20:59 firefox_55.0-1_55.0-2_amd64.debdelta
> -rw-r--r-- 1 jak jak 2.4M Aug 15 22:13 firefox_55.0-1_55.0-2_amd64.pdeb
and bsdfiff of old data.tar vs new data.dat 2.3MiB which is probably
what debdelta does. So I am not sure if it is worth the extra mile to
diff file by file. It might be faster and less memory hungry however.
> # Further extensions
> If you put a pristine-tar delta into the delta file, you can fully
> reconstruct debs.
There is deltarpm  which does the same thing for rpm/fedora. I tried
to find a design document but it seems that there is none. It seems
however they grab all the binaries and make a delta via in-tree copy of
bsdiff (delta.c). They also have intree-zlib but I didn't look why…
I was mostly interrested if they have some filters to replace the
offsets in binaries with something else but didn't find anything yet.
I am not sure if they keep old rpm around for the delta to apply or if
they reconstruct if from the file system (minus the config files).