On Sep 20, 2010, at 11:40 AM, Domen Kožar wrote: > Thanks. Just to be sure, there is no need to handle rollback case when > before_flush is called?
If before_flush() fails, the transaction isn't affected by the exception thrown. The subtransaction doesn't begin until later in the flush() method. So after the exception thrown, the session is in whatever state your before_flush() left it. If that's state you want to throw away, its typical (at least recommended) that Sessions are always used in an outermost enclosing block that will rollback() after an exception is thrown. But the before_flush() exception is not different from if end-user code threw an exception before flush() was called. > > On Sep 20, 5:35 pm, Michael Bayer <mike...@zzzcomputing.com> wrote: >> On Sep 20, 2010, at 11:29 AM, Domen Kožar wrote: >> >>> I'm writing simple glue layer between Whoosh and SQLAlchemy, the idea >>> is that session event system reflects update of search index in whoosh >>> (using celery). >> >>> Looking at versioning example, it relies on before_flush event and >>> make a snapshot. I need something similar, probably more complex. Here >>> are the questions: >> >>> - how to handle exceptions and rollbacks for changes done in >>> before_flush >> >> just throw the exceptions outward, its another flush failure case. >> >>> - does before_flush also handle bulk updates/deletes >> >> use after_bulk_update() / after_bulk_delete() >> >>> - how to distinct new objects from existing in db (from session state) >> >> obj in session.new >> >>> - maybe before_flush is not the best event? >> >> its usually the best place to do things. >> >> 0.7 will move to this interface (The extension interfaces will remain around >> for quite some time, at least throughout 0.8): >> >> from sqlalchemy import event >> >> # Session can be the Session class (global), a scoped_session, >> # a sessionmaker(), a session >> event.listen(my_before_flush, "on_before_flush", Session) >> >> # filter for certain classes in the flush >> event.listen(my_before_flush, "on_before_flush", MyClass) > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To post to this group, send email to sqlalch...@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. > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@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.
