[squeak-dev] Re: Our process, some loose ideas regarding DS + MC

Göran Krampe goran at krampe.se
Sun Aug 16 11:32:25 UTC 2009


Hi!

Igor Stasenko wrote:
> 2009/8/16 Andreas Raab <andreas.raab at gmx.de>:
>> Which reminds me: Where are the deltas stored and how big is the space
>> overhead for keeping them?
>
> i think most common overhead is 2x more space comparing to analoguous
> changeset record, since you have to keep 'before' version in addition
> to 'after' version. And most common change is changing the method(s)
> source a little bit.

Well, in fact it is more - a Changeset does in fact not hold a copy of 
the new method source - just a pointer to the method modified (IIRC).

Thus Changesets are sneaky beasts, most people get the wrong impression.

> Oh, and did Goran mentioned that Deltas could be also 'compressed' in
> same way as changeset?

Yes, I have called it "normalized" but compressed may be a better term.

That code is not yet finished though, but a fun coding task for anyone 
interested. :) There are two scenarios:

- Compressing a single Delta into its non redundant form. This makes it 
look like a Changeset. Before compression it is a "perfect" log.

- Compression of multiple Deltas into one. This one is trivial once you 
implemented first one.

For bug fixes and patches I believe one would naturally want to compress 
before distributing of course.

regards, Göran




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