On Tue, Aug 10, 2010 at 11:31, Hyrum K. Wright <hyrum_wri...@mail.utexas.edu> wrote: > On Tue, Aug 10, 2010 at 10:26 AM, Julian Foad <julian.f...@wandisco.com> > wrote: >> On Tue, 2010-08-10 at 15:31 +0100, Julian Foad wrote: >>> Upgrading a WC to single-DB: >>> >>> upgrade_to_wcng() calls >>> >>> svn_wc__db_upgrade_begin() to create a new DB, and then >>> svn_wc__db_wclock_obtain() and then >>> svn_wc__write_upgraded_entries() >>> >>> The _wclock_obtain() fails because it checks that the node with relpath >>> "" exists. Normally in libsvn_wc a new DB is created with >>> svn_wc__db_init() which inserts a row for relpath "", but >>> svn_wc__db_upgrade_begin() doesn't. >>> >>> What's the best solution here? Not lock it? Have >>> svn_wc__db_upgrade_begin() create an initial "" row? Have >>> svn_wc__db_wclock_obtain() NOT check for existence of a "" row? The >>> first and last options don't sound right. Creating an initial "" row >>> does sound right, and requires (presumably) a modification of >>> svn_wc__write_upgraded_entries(). >> >> The upgrade function is creating new DBs (or a new single-DB). Should >> it perhaps be asking for a lock on the DB as a whole, as distinct from a >> recursive lock on the WC root directory? In normal operation, those two >> mean the same, but maybe here we need to distinguish these as two >> different concepts. > > Where is the upgrade DB being created? If it's called something like > 'wc.db.foo', I would think you don't require *any* locking, since no > other process is going to be looking for that file. Do the upgrade, > and then move it in to place before nuking all the old data.
At the moment, it is called 'wc.db'. IIRC, there were some issues where wc_db calls were made and it looked for wc.db. Not sure if that is still true (ideally, there would be NO wc_db calls during an upgrade process). So... locking is still needed. Maybe we should allow locks on non-existent rows. Effectively a "reservation" that something is about to create that row. Cheers, -g
