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Re: [Issue 1585] Deltified dumps for archival and schema conversion

From: Branko Čibej <brane_at_xbc.nu>
Date: 2004-06-19 14:38:54 CEST

Mikhail Terekhov wrote:

> I thought that convert one kind of delta to another is much less
> expensive than calculate it anew, plus huge savings in space.

There's a huge misconception here. CVS uses context diffs (diff -e, I
believe). Subversion uses a block-copying, compressing binary delta
algorithm. The most efficient way to "convert" from one to the other is
simply to recreate the fulltext from CVS and calculate the delta in SVN.
I suppose we could convert directly, but the results wouldn't be that good.

As for using deltas in the dumps -- "svnadmin load" won't simply store
those back into the repository. It'll recreate the current fulltext and
apply that. The deltas are for space, not time efficiency.

Last but not lease, you convert your CVS repository to Subversion
exactly once. If it takes 10 days, we can probably shave off some of
that time, but it's only once, after all. What you can do is start using
Subversion immediately, importing a snapshot of the current state from
CVS. Then convert the CVS repository, however long that takes. Then do
an incremental dump of the SVN repository (from just after the import)
and load that on top of the converted CVS repository. In that way you
don't have to stop work during repository conversion, you just don't
have access to history in SVN while the conversion is going on (but _do_
have access in CVS, of course). That's not too bad, is it?

-- Brane

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Received on Sat Jun 19 14:39:23 2004

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