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Re: [PATCH] Skip-deltas, for review

From: Greg Hudson <ghudson_at_MIT.EDU>
Date: 2002-07-27 02:47:03 CEST

On Fri, 2002-07-26 at 20:01, Karl Fogel wrote:
> Hmmm. I hate to say it after the work you've done, but with these
> numbers it's hard to see why Subversion should incorporate this
> change.

Well, that's a reasonable position to have, but our repository might be
a deceptively simple case. As I noted in my first message, Branko's
delta combiner doesn't actually seem to improve the speed of day-to-day
operations in my tests either, when operating on our repository. (It
does fix the deltifying-files-larger-than-chunk-size bug, because he
rewrote the relevant piece of code, but that bug could certainly be
fixed without introducing such a huge piece of machinery.)

As repositories get larger or use patterns focus on smaller numbers of
files, though, both the delta combiner and skip-deltas become more
relevant to daily life.

> Am I missing something? I haven't looked over the patch; if you feel
> it actually makes the code *simpler*, or brings some benefit I haven't
> noticed, then that's different. Just based on the above, though, I
> don't see how it helps us...

It doesn't make the code notably more complicated. A few lines added
here and there to maintain the predecessor count, a short function added
to tree.c to do the skip deltas, and some no-longer-desirable code
removed from reps-strings.c. The net effect on code complexity is tiny.

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Received on Sat Jul 27 02:47:38 2002

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