Re: .deb format: let's use 0.939, zstd, drop bzip2

[Ansgar <ansgar@debian.org>]

Adam Borowski writes:
> On Mon, May 13, 2019 at 11:25:11AM +0200, Ansgar wrote:
>> It supports solid compression[1] which
>> compresses multiple files into one block like tar.xz, but unlike tar.xz
>> can use more than one block: "Later versions of 7-zip use a variable
>> solid block size, so that only a limited amount of data must be
>> processed in order to extract one file".
>
> Yeah but the default block size is 2GB, which would make every single .deb
> in the archive effectively fully solid.  You can fine-tune the values, but
> example numbers don't appear like they'd help much.
>
> And just tested, -ms=on vs -ms=16m:
> -rw-r--r--  1 kilobyte kilobyte 1087957645 May 13 14:37 u.7z
> -rw-r--r--  1 kilobyte kilobyte 1253369019 May 13 14:50 u16m.7z
>
> So the space loss is massive.

That indeed looks like it likely not worth switching to a different
format to allow better random access (which is more of a special-use
case anyway).

Thank you for your experiments!

Ansgar