Re: A look at some alternative PACK file encodings
- From
Shawn Pearce <spearce@spearce.org>
- Date
- Sep 7, 2006, 05:41 UTC
- Message-ID
- <20060907054126.GC31580@spearce.org>
- In-Reply-To
- <9e4733910609061704s429c449etcf0475841556c26b@mail.gmail.com>
Jon Smirl <jonsmirl@gmail.com> wrote:
> The repack code could build a model of the tree as it is repacking, > that is what fast-import does. If you have a model of the tree then > when you change a TREE node you track the last sha1 that corresponded > to that directory path. Now you know what to diff to.
Right. But that's horribly expensive. For the most part pack-objects does a good job estimating this by hashing the trees by their name and size into the same hash bucket. And its fast.
Besides its better to store reverse deltas (like what CVS does) as faster access to the more recent stuff is more interesting than faster access to the older stuff. pack-objects tries to do this based on the order given by rev-list.
-- Shawn.