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Re: major Subversion progress

From: Timothee Besset <timo_at_qeradiant.com>
Date: 2001-07-13 08:48:54 CEST

That's great news!

I'm waiting for the first "usable" version with a cvs2svn repository to start playing with it. But actually, is it planned to have some svn2cvs feature? I can conceive that it has not a lot of interest for you guys, but since there won't be a lot of SVN clients in the first versions (specially graphical ones), I don't think I would be able to get all my developers to make the switch..

TTimo

On Thu, 12 Jul 2001 17:38:44 -0500
Karl Fogel <kfogel@collab.net> wrote:

> I know not everyone is following the CVS commit mails closely, so I'd
> like to point out that something totally awesome just happened:
>
> The Subversion repository now does deltified storage. In other words,
> we can take our filesystem code seriously now! :-) Big-time kudos to
> Mike Pilato <cmpilato@collab.net> for finishing this one off.
>
> This was the last truly major coding task on the todo list, as far as
> Subversion itself goes -- everything else we need to get to alpha is
> relatively small: keyword substitution and newline conversion, some
> fixes in the working copy code, etc. Some things, like the hook and
> auth systems, need some more design think-time, but once designed,
> they are easy to implement.
>
> A couple of notes:
>
> 1. There is still one big thing that needs to happen before M3: a
> cvs2svn repository converter :-). If anyone wants to volunteer,
> that would be a fine thing... You wouldn't be all alone: many
> on this list have a good understanding of how the converter
> needs to work, and various ways to make it efficient. The main
> reason this is a big task is that the converter needs to have a
> *very* thorough test suite, because (obviously) we can't afford
> to corrupt data.
>
> 2. The deltification code still has room for improvement. While
> the conversion from fulltext to delta is quite efficient
> (probably only minor improvements are possible from here), the
> undeltification code will probably want tweaking at some point
> in the future. Currently, fulltext reconstruction uses memory
> proportional to the delta window size times the number of
> intermediate deltas between the target and the "base" fulltext
> (the latter usually being the most recent revision of the
> object); there are also some running time issues.
>
> Regarding (2):
>
> Mike, Ben, and I all feel is that it would be premature optimization
> to write the Ultimate Efficient Delta Combiner at this time, when
> there are so many other important tasks that need doing. It is
> perfectly acceptable to get to 1.0 with the undeltification method we
> have now, which should perform well enough in most circumstances.
>
> Doing real delta combination will get us a big-O improvement for
> retrieving large files, and we more or less know how to do it.
> However, it is a very complex coding task and IOHO it's more important
> to get Subversion to feature-completeness than to optimize every last
> drop out of the delta reconstruction algorithm. (This is not intended
> to discourage others from working on it right now if they want, of
> course!)
>
> With all this in mind:
>
> Mike and I are going to spend tomorrow writing a slew of new fs tests,
> whose goal will be to stress the new deltified storage code, and make
> sure it performs acceptably at least where CVS performs acceptably.
> Then starting Monday, we're going to bid the deltification code adieu
> and join everyone else on the rest of alpha-checklist.txt. The goal
> is to get foolproof regression insurance in place and then move on.
> That way, when we later do improve the algorithm, we will know right
> away if it works and won't need to worry about whether it's
> functionally equivalent to the old code.
>
> Okay, enough happy-talk, clearly there's still a lot of code to write.
> Back to work now... Keep those patches coming!
>
> -K
>
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Received on Sat Oct 21 14:36:33 2006

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