How many Ubuntu branches share history with upstream?

John Arbash Meinel john at
Wed Feb 10 16:27:21 GMT 2010

Hash: SHA1

James Westby wrote:
> On Wed, 10 Feb 2010 08:46:37 -0600, John Arbash Meinel <john at> wrote:
>> Where is this script going to be running? I wrote a trivial command that
>> lets you run:
>>   bzr in-ancestry branch1 branch2
>> And reports back if the ancestry of branch1 is in branch2.
>>   lp:~jameinel/+junk/bzr-in-ancestry
>> Running locally on trees, it takes less than 3 seconds to return
>> true/false. Note also that the answer isn't symmetric. We've merged
>> plugins into, but those plugins have not merged into them.
>> Similarly for packaging branches. I would imagine that the packaging
>> branch might merge upstream, but not the other way around.
>> Comparing a mysql branch with a one seems to take 4s, which
>> still isn't particularly long. I don't know what time scale you were
>> hoping for
> Certainly less than a day to run. 3s * 10,000 ~= 8 hours. It wouldn't be
> near that to start with as we don't have anywhere near that number of
> packaging links, but it's always useful to look at what would happen if
> you scale.

Well, you can also run it as parallel as you want to. Given that you are
acting against 10k entries. Going further, if you *really* wanted to
scale, then you would want to look at whether you need to regenerate all
10k projects from scratch every day. I would be surprised if
a) A project that does have the ancestry suddenly stops having the
b) A project with no new commits in the packaging branch starts
   including ancestry
c) All 10k branches would have new commits every day.

As always, the way to scale to N is to avoid doing this O(N) :).

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