Re: topological index field for commit objects

From: Marc Strapetz <marc.strapetz@syntevo.com>
Date: Jul 1, 2016, 06:45 UTC
Message-ID: <df4f72c0-72fc-a779-3fda-3fbc146419db@syntevo.com>
In-Reply-To: <20160701031711.GA4832@sigill.intra.peff.net>

On 01.07.2016 05:17, Jeff King wrote:

Show 12 quoted lines

> On Thu, Jun 30, 2016 at 11:12:52AM -0700, Linus Torvalds wrote:
>
>> I do think that it's ok to cache generation numbers somewhere if there
>> is an algorithm that can make use of them, but every time this comes
>> up, it's just not been important enough to make a big deal and a new
>> incompatible object format for it. The committer date is preexisting
>> and has existing pseudo-generation-number usage, so..improving on the
>> quality of it sounds like a good idea.
>
> If you are OK with a cache, I don't think one needs to change the object
> format at all. It can be computed on the fly, and is purely a local
> optimization.

What I like about the local cache is that it can be fixed easily: if we had generation numbers already, there would certainly be a few repositories now which would violate the parent - child condition (however that has happened) and then you have to deal with this scenario anyway (or tell the user to rewrite his entire history). It's a lot easier to throw away and rebuild the cache.

Also, the local cache can be improved over time, starting with generation numbers now and one day supporting a FELINE index or whatever will come.

-Marc