On Thu, Apr 19, 2012 at 07:32:15PM +0200, Bernhard M. Wiedemann wrote: > On 04/12/2012 02:35 PM, J. Daniel Schmidt wrote: > > Dear Developers, > > > > While testing our SUSE OpenStack packages we hit a nasty bug and > > reported it as: https://bugs.launchpad.net/keystone/+bug/972502 > > > > We found out that the underlying cause was a lack of referential > > integrity[1] using sqlite or mysql. When we tried to reproduce this > > issue on postgresql the usage of foreign keys greatly helped to > > find the cause. > > > > In order to prevent further inconsistencies we created a patch that > > added more foreign keys: https://review.openstack.org/6216 > > > > One reviewer commented: > >> i don't approve of adding foreign keys, and we should probably > >> remove the existing ones (in UserTenantMembership and in > >> Endpoint) > > > > and on > > https://review.openstack.org/#patch,sidebyside,6216,3,keystone/identity/backends/sql.py > >> > > > we shouldn't be using foreign keys at all, they are a crutch that are not > >> available everywhere > > > > This was a surprising answer to us as the usage of the foreign keys > > revealed the inconsistency in the first place. So removing them > > elsewhere does in no way improve the situation, it even does not > > help for mysql and sqlite, as SQLAlchemy abstracts them away. We > > also found similar bugs elsewhere: > > > > * https://bugs.launchpad.net/keystone/+bug/959294 * > > https://bugs.launchpad.net/keystone/+bug/973243 * > > https://bugs.launchpad.net/keystone/+bug/974199 > > > > In our point of view foreign keys should be used in all possible > > places. This would not harm any database that does not support them > > but helps all of us to find data inconsistencies and related bugs, > > which leads to faster development with fewer bugs. > > > > > > What is your take on these things? How would you take care of data > > consistency otherwise? > > > > > > Thank you for your feedback, Berhard M. Wiedemann J. Daniel > > Schmidt > > > > [1]: http://en.wikipedia.org/wiki/Referential_integrity > > > Just saw another bug, that would have been caught earlier with foreign > keys: > https://bugs.launchpad.net/nova/+bug/754900 > > So was this issue discussed on the OpenStack Summit?
Yes, I raised this in the "Standardizing database management across projects"[1] session and everybody attending that sessions agreed that it's a good idea. However, https://review.openstack.org/#/c/6216/ is still open ;( Best Christoph [1] http://folsomdesignsummit2012.sched.org/event/40adf6c240f7ed1fab82e19e8e55dc24 -- Christoph Thiel, Project Manager, SUSE Cloud Infrastructure SUSE LINUX Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 16746 (AG Nürnberg) _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : openstack@lists.launchpad.net Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
