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Re: [Issue 4081] incremental svnadmin hotcopy for BDB-backed repositories

From: C. Michael Pilato <cmpilato_at_collab.net>
Date: Thu, 15 Dec 2011 11:08:25 -0500

On 12/15/2011 10:24 AM, Daniel Shahaf wrote:
> That's an interesting approach. But can we do without the log files?
> Is there an easy way to, given N, capture all the table rows that belong
> to revisions youngest than rN?

I suppose that depends on what you mean by "easy". We'd need a whole bunch
of custom code on both the read and write side of things.

> (And would we ever need to delete DB rows from the hotcopy? The above
> algorithm assumes append-only tables.)

No, we cannot maintain an perfect row-by-row copy in append-only mode.

At a minimum we have to deal with deltification, which for older BDB formats
happens constantly in already-committed revisions, and for newer formats can
also occur at the administrator's request. But that's a storage detail, and
(I think) doesn't affect the semantic sanity of such a backup.

More pressing is the matter of revision properties, which of course can
change at any time. (How did the FSFS code handle that one, even?)

FWIW, the logfile approach also wouldn't provide append-only operation at
the BDB table level. I'm not quite sure where this append-only requirement
is coming from, though.

C. Michael Pilato <cmpilato_at_collab.net>
CollabNet   <>   www.collab.net   <>   Distributed Development On Demand

Received on 2011-12-15 17:09:04 CET

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