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Re: svn.collab.net is going down...

From: Branko ╚ibej <brane_at_xbc.nu>
Date: 2002-06-18 02:25:25 CEST

Greg Hudson wrote:

>On Mon, 2002-06-17 at 13:37, Branko ╚ibej wrote:
>
>
>>It makes the delta combiner waaay simpler if I can assume that, when
>>combining two windows A and B, the length of the target view produced by
>>A is the same as the length of the source view expected by B, and that
>>A's target view starts at B'a source view offset.
>>
>>
>
>Hm. I see. Otherwise the source windows can grow very large. In the
>current scheme of things, if you apply ten deltas in sequence to get
>from A to K, then in theory the first block of K might depend on data
>from anywhere in the first 11*winsize bytes of A. (You have to produce
>two windows of J to build the source window for K; you have to produce
>three windows of I to build two windows of J; etc.) So I'm not sure
>this problem is solvable even in the long term, at least with reasonably
>streamy behavior.
>
Something like that, yes.

>On the other hand, it's kind of a bummer not to have any slop in the
>source windows. With no slop, if I add a 300-byte paragraph to the
>beginning of a large text file, there will be roughly 300 bytes of stuff
>to insert in each window of the diff. Maybe not so big a deal as long
>as the window size is reasonably large.
>
That, and the fact that whatever data is shifted gets compressed by
vdelta, too. And Daniel's patch will compress the svndiff even more, so
we probably end up even in general.

We can always bump the delta window from 100k to 1M if it becomes a
problem, but i don't think it will. Sure, anybody using subversion as a
backing store for her video post-processing lab is in for a shock. :-)

>[About Daniel's work:]
>
>
>>I think it should go in.
>>
>>
>
>I like it too; I just didn't think he thought it was ready yet.
>
I'll ask him before I touch it.

-- 
Brane ╚ibej   <brane_at_xbc.nu>   http://www.xbc.nu/brane/
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Received on Tue Jun 18 02:26:02 2002

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