2009/8/16 Göran Krampe <goran at krampe.se>:
> 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).
>
oh, i meant not in-image space, but storage space required for
interchange format.

> Thus Changesets are sneaky beasts, most people get the wrong impression.
>
yes, and we could do same with deltas - use external storage for
keeping them in file(s), while in-image
they hold only a pointers.
But i think its too early to think about it.
Or.. why too early?
You already mentioned different ways to persist the deltas.. so
a delta 'pointer' could be represented by a tuple: (adaptor , id)

where adaptor could be: file, couch DB, url or anything else,
and id is an additional info , identifying given delta.

Or, just use a common denominator of all of this stuff - URI.
I don't think that its hard to introduce a new URI, which identifies a
Couch DB storage :)


>> 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.
>

Right

> regards, Göran
>
>
>



-- 
Best regards,
Igor Stasenko AKA sig.