Torsten Irländer <torsten.irlaen...@googlemail.com> wrote:
> > > Am Donnerstag, 12. Februar 2015 18:57:43 UTC+1 schrieb Michael Bayer: > > > Torsten Irländer <torsten....@googlemail.com> wrote: > > > Hi, > > > > I have a similar prolem as described in > > https://groups.google.com/forum/#!topic/sqlalchemy/OLeCERDZxyk > > > > I am using the secondary attribute to define the many-to-many relationship > > between User and Groups. > > > > Now i want prevent to delete a group if a user is still in the group. > > Setting the Foreign-Key to "nullable=False" as advised in the post above > > does not work for me on SQLAlchemy level. It does work when trying to > > delete the Group directly in Postgres (Error ist raised). I am using no > > cascading deletes in the relation definition. > > when you say “prevent”, do you mean, session.delete() will silently do > nothing, or that an error is raised (or how exactly are these deletes > originating)? If the database is set up with constraints as you describe, > then it would raise constraint violations. Or are you looking for some > error message to be raised sooner? > > Prevent means raise an error which could be excepted (and optionally > analysed) to show the user some feedback that the deletion of the groups can > not be done because there are still referencing objects. > The deletion is done by a session.delete(). What’s wrong with the IntegrityException here? Not specific enough? I’d recommend parsing the string message within it to determine its cause - this is a feasible approach that we use widely with openstack. The exceptions that relate to this particular violation will be predictable. The database does a great job of catching this error, so efforts for SQLAlchemy to do the same thing would be redundant. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
