Re: Complexity of creating a new revision.

On Sun, 23 Oct 2005 18:50:57 +0200
Miha Vitorovic <mvitorovic@nil.si> wrote:

> > the vector of trees is not stored as complete copies in the repository,
> > it's encoded as a series of "deltas"
> > so when you use the FSFS or the BDB backend, you have to read/adjust
> > O(log(n)) deltas (according to svn/trunk/notes/skip-deltas )
> > so this is *not* done in constant time, right ?
>
> Not as I understand it. To recreate the contents of a given revision, sure
> you need to go through all the diffs, to get it. But to create a copy of a
> given tree at revision X, all you need to do is "create copy of a tree at
> revision X", that is you create a new reference to the data, without
> actually copying or recreating that data. That will be done, when somebody
> tries to read the contents of this copy. I guess in the context of a *nix
> FS, this would be like a hard link to a directory.

yes, only a new reference must be created pointing to the data , but since this new reference adds a new revision, it must be encoded as a delta against a previous one (in the fsfs case) or some deltas must be recreated (in the bdb case)
no ?

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