From: Marc Strapetz Date: Fri, 01 Jul 2016 06:45:33 GMT Subject: Re: topological index field for commit objects Message-ID: In-Reply-To: <20160701031711.GA4832@sigill.intra.peff.net> On 01.07.2016 05:17, Jeff King wrote: > 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