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Re: [RFC] issue 2286 - space saving in the repository

From: Malcolm Rowe <malcolm-svn-dev_at_farside.org.uk>
Date: 2006-05-20 17:06:10 CEST

On Sat, May 20, 2006 at 03:47:07PM +0100, Max Bowsher wrote:
> Hang on a moment: in real disk filesystems, once a hardlink has been
> made, there is _no_ evidence which was the original filename and which
> was the linked filename. I see no reason why the same should not be
> true for Subversion. In both BDB and FSFS repositories, the history
> storage and content storage are very decoupled, with nodes referring to
> their content using only 1 (BDB) or a few (FSFS) numbers - numbers which
> could likely simply be duplicated when storing a new node-revision
> containing the same content as a previous one.
>

I looked at doing something similar a few months back (hardlinking
identical representation inside FSFS). I was put off by the fact that it
was impossible to do it streamily (you'd need to rewrite the rev file,
which wasn't something I was happy doing as an online operation) and
also because the FSFS backend at least seems to use the representation
key as a way to determine whether two nodes are 'the same' - and it's
not immediately clear whether the kind of sameness is one that should
also be true for hard-linked nodes.

Regards,
Malcolm

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Received on Sat May 20 17:06:35 2006

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