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Re: Large repository with a long checkout problem

From: Alan Barrett <apb_at_cequrux.com>
Date: 2006-08-06 11:06:13 CEST

On Sat, 05 Aug 2006, Les Mikesell wrote:
> [slow checkout]
> However, is this an artifact of conversion or where everyone is headed
> with subversion after a few years as a result of the design decision
> to reconstruct from the oldest rev and deltas every time instead
> of maintaining the most recent and applying delta's backwards like
> rcs/cvs do it?

Reconstructing files from deltas is probably cheaper than you expect,
because of the skip-delta storage scheme. See notes/skip-deltas in the
subversion source tree. The number of deltas that need to be applied
is O(log(number of changes)). With the FSFS backend, it's equal to
the number of "1" bits in the binary representation of the number of
changes. The "number of changes" above is the number of changes to a
particular file, not the global repository revision number.

I'd expect checkout times to be correlated more strongly with the
number of files and directories in the checkout, and the total size of
the checkout, with only a weak correlation with the total size of the

--apb (Alan Barrett)

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Received on Sun Aug 6 11:08:40 2006

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