phrrn...@googlemail.com wrote: > You are correct: the code-snippet will cause an exception to be thrown > when SA attempts to flush any changes. However, the connection > callable is called *per-instance* and it is supposed to return the > connection to use to perform the flush. Inside the callable, you can > peek at the mapper and/or the instance and return whatever you deem > appropriate.
Ah, I see, so instances can have some say in the decision making. > What kind of failure mode are you looking for? If you > have a session with forbidden writes, what should happen? Nothing gets > written? The legitimate updates occur but the disallowed ones generate > exceptions? disallowed writes are silently swallowed by a mock > connection (probably make programmers very upset, confused and angry!) I think nothing at all should be committed, and an exception should be raised to the application. > The problem with any of these approches is -- as you point out -- that > the application is not informed of the boo-boo at the time it occurs. > I wonder what Michael is alluding to in his comment about implementing > __getattribute__? I assume he meant __setattr__? I'm not sure, I haven't had a chance to think about it much yet. I'd be all right if indeed the failure only occurred at the end of the transaction during a commit, if at least the error message is clear. The most important bit is to prevent the developer from updating a record that really shouldn't be updated (instead the developer should first create a new editable version of the record). Preferable of course would be if we could do this validation earlier. The validator approach in SQLAlchemy allows this, but you'd need to set it manually for every mapped attribute, while I'd like to register one validator for every mapped attribute... Regards, Martijn --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
