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RE: Two svn_wc__db_t for single-db upgrade

From: Bert Huijben <bert_at_vmoo.com>
Date: Thu, 26 Aug 2010 16:58:44 +0200

> -----Original Message-----
> From: Philip Martin [mailto:philip.martin_at_wandisco.com]
> Sent: donderdag 26 augustus 2010 16:34
> To: dev_at_subversion.apache.org
> Subject: Two svn_wc__db_t for single-db upgrade
> One of the problems with single-db upgrade is that write_entry, called
> from svn_wc__write_upgraded_entries, want's to be able to query the
> new database using things like svn_wc__db_scan_addition. This fails
> because svn_wc__db_pdh_parse_local_abspath encounters old .svn dirs
> and creates pdhs with the wrong wcroot.
> One way to fix this would be to revamp write_entry so that it doesn't
> need to query the existing database, but that would involve caching in
> memory some of the stuff we write to the database.

I think this code needs revamping anyway, to properly calculate op_depths
and other things we need for the 4th tree that will never be returned by
just calling read_info().

I think the upgrade code should just read the entries in a directory and
then upgrade the nodes it sees, passing a chain of parent entries (or
similar) so you never have to rely on the intermediate DB state while
loading. (This also avoids actively maintaining the upgrade code in future

The normal recursive iterpool pattern should keep the amount of in memory
data manageable. (Shouldn't be much more than an old svn_wc_walk_entries
call + the upgrade state).

> An alternative is to use two svn_wc__db_t handles and arrange for one
> of them to ignore the old .svn directories. The following patch does
> this and passes the upgrade regression tests (admittedly not much of a
> test). Does this sound like a good approach?

Thinking about the 4th tree, I think this will work now, but break in only a
few weeks.

A slightly easier variant (that needs less hacks) might be to create the
wc.db in a temp directory, like you recently implemented for 'svn copy
wc-dir wc-dir2'.

Received on 2010-08-26 17:00:01 CEST

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