Re: [PATCH] add the ability to create and retrieve delta objects

From: Chris Mason <mason@suse.com>
Date: May 3, 2005, 11:24 UTC
Message-ID: <200505030724.57827.mason@suse.com>
In-Reply-To: <Pine.LNX.4.62.0505030344170.14033@localhost.localdomain>

On Tuesday 03 May 2005 04:06, Nicolas Pitre wrote:

Show 9 quoted lines

> On Mon, 2 May 2005, Linus Torvalds wrote:
> > If you do something like this, you want such a delta-blob to be named by
> > the sha1 of the result, so that things that refer to it can transparently
> > see either the original blob _or_ the "deltified" one, and will never
> > care.
>
> Yep, that's what I've done last weekend (and just made it actually
> work since people are getting interested).
>

This looks much nicer than using zdelta, I'll try switching my packed item to your delta generator later this week. Some quick and dirty space numbers to show why we need to pack the files together:

On the full import of all the bk->cvs changesets, the average file size in .git is 4074 bytes. 73% of the files are 4096 bytes or smaller.

This means that of the 2.5GB the .git directory consumes, about 1GB is taken up by files under 4k where deltas won't save space. If the remaining files could be delta compressed down to less than 4k, they would still take up around 400MB on disk.

-chris