Re: Large repository with a long checkout problem

On 8/6/06, Alan Barrett <apb@cequrux.com> wrote:
> 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
> repository.
>

I had thought that that could be true which is why I did an export of
the HEAD revision and used it to create a new repository. This way the
checkout size/number of files is the same. The difference in checkout
times was 5.5 min down to 1.5 min. Of course, I don't think it is so
much a relation to the aggregate size of the repo, as much as the
number of diffs of the particular files in the checkout...which seem
to be quite a few in this case.
> --apb (Alan Barrett)
>
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>

I guess that the best solution is probably going to be to use BDB. So
is the "wedged" state really only caused by broken connection in the
middle of commits (power outage, connection breakages, etc?) because
if that is the case, then I guess that won't happen to often and
should not cause an adminatration headache.

Thanks for all of ya'lls input.

Troy

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