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Re: do away with db/revprops/*/, and a question about 'upgrade' concurrency (was: Re: Does fsfs revprop packing no longer allow usage of traditional backup software?)

From: Hyrum K Wright <hyrum_at_hyrumwright.org>
Date: Fri, 1 Jul 2011 11:21:58 -0500

On Fri, Jul 1, 2011 at 8:05 AM, Daniel Shahaf <danielsh_at_elego.de> wrote:
> Hyrum K Wright wrote on Thu, Jun 30, 2011 at 16:33:16 -0500:
>> On Thu, Jun 30, 2011 at 3:27 PM, Peter Samuelson <peter_at_p12n.org> wrote:
>> >
>> > [Ivan Zhakov]
>> >> It should be easy to implement editing revprops without using SQLite:
>> >> in case someone modify revprop non-packed revprop file is created, in
>> >> read operation non-packed revprop file should be considered as more
>> >> up-to-date. In next svnadmin pack operation these non-packed files
>> >> should be merged back to packed one.
>> >
>> > +1.  This would basically mean there's only _one_ code path for writing
>> > revprops, yes?  'svnadmin pack' gets a little more complex, but the
>> > rest of libsvn_fs_fs gets simpler.
>> >
>> > Anyone have time to actually do this?  Converting the packed format
>> > from sqlite to the same format used for packed revs would be a bonus.
>>
>> I like this idea, but it would seem to introduce an additional stat()
>> call* for every attempt to fetch a revprop, because you'd first have
>> to check the "old" location, and then the packed one.
>
> I don't like the idea of writing revprops outside the DB and moving them
> back in. (I think I already said why elsethread?)

(I will assume "the DB" means "the SQLite-backed revprop database".)

I agree with you, but I don't think that's what the proposal was
about. My understanding would be that we'd pack revprops just like we
pack revision (one single concat'd file per shard), and then store any
edits in separate files. We'd then "repack" the edits into the pack
files when an admin subsequently runs 'svnadmin pack'.

Aside from the complexity of having to attempt to open the non-packed
file everywhere before failing through to the common case, I really
like this solution. (So much so that I may go implement it...)

-Hyrum
Received on 2011-07-01 18:22:33 CEST

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