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Re: [Subversion Wiki] Update of "StarDelta" by StefanFuhrmann

From: Daniel Shahaf <danielsh_at_elego.de>
Date: Wed, 19 Sep 2012 09:53:14 +0100

Apache subversion Wiki wrote on Tue, Sep 18, 2012 at 23:30:26 -0000:
> Dear Wiki user,
>
> You have subscribed to a wiki page or wiki category on "Subversion Wiki" for change notification.
>
> The "StarDelta" page has been changed by StefanFuhrmann:
> http://wiki.apache.org/subversion/StarDelta
>
> Comment:
> WIP. first part
>
> New page:
> = Star Deltas =
>
> == Introduction ==
>
> FSFS currently uses xdelta to store different version of the same node efficiently.
> Basically, we represent node x_i as
>
> x_i = x_i-1 o \delta(x_i, x_i-1)
> x_i-1 = x_i-2 o \delta(x_i-1, x_i-2)
> ...
> x_0 = x_0
>
> and store x_0 plus the incremental \delta information. x_i gets reconstructed by
> starting with x_0 and iteratively applying all deltas. Assuming that size(x_i) is
> roughly proportional to i and the deltas averaging around some constant value,

This assumption means that every commit to a file increases its size by
948 bytes (or some other constant number that depends only on the
node-id). I don't think that's how software development (one use-case
of svn) works. Do you have real world data to corroborate your
assumption? Or perhaps a use case that would trigger such behaviour?
Received on 2012-09-19 10:54:02 CEST

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