compressed weaves, and revision.weave

[John A Meinel]

Martin Pool wrote:
> On 25/10/05, John Arbash Meinel <john at arbash-meinel.com> wrote:
>
> I think compressing the storage is a good idea, but I'd like to switch
> to an append-only indexed weave-like format at some time in the
> future.  I have the start of some code for that here.
>
>   http://people.ubuntu.com/~mbp/bzr.mbp.knit/
>
> There is some tension between such a format and compression; I suppose
> we could just compress each appended record of the file independently.
>  The ratio might not be as good but it would eliminate some text
> redundancy, and I suppose we can rely on the delta compression to get
> some more.
>
> I think I'd like compression to be optional; for local access the CPU
> cost may be more than people wish to pay.

I believe I have implemented it, I was able to upgrade the bzr.dev tree.
But I didn't write any more tests.

I made compression optional by having a ".bzr/compressed" file. And then
"bzr upgrade" takes "--compress" or "--uncompress" flag.

I also implemented conversion to using a revision.weave file (and using
the alternate inventory and revision formatting) using bzr upgrade.

>
> It might make sense to do compressed weaves as an intermediate step.
>
> Storing the revisions and signatures in there is also a good idea.

I would like to see the indexed form as well. Though there are a few
ways to do some compression along with the indexing.

As others have mentioned, I'm not sure how much compression you can get
versus the extra headers that get added. But I'm sure you could get
something from compression.

John
=:->

>
> --
> Martin
>
>

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