moggie wrote: > Greetings, > > Hope you are well. In my example I have two objects 'HttpTest' and > 'SmtpTest' that both inherit from their super-class called 'Test'. > > Due to the nature of the relationship, 'Test' will never actually be > stored in the database so I've not mapped that. However, a mixture of > 'HttpTest' and 'SmtpTest' objects are both to be stored in the > hosttest_table, thus I created a mapping for them like this: > > httptest_mapper = mapper(HttpTest, hosttest_table, \ > polymorphic_on=hosttest_table.c.type, > polymorphic_identity='http') > smtptest_mapper = mapper(SmtpTest, hosttest_table, \ > polymorphic_on=hosttest_table.c.type, > polymorphic_identity='smtp') > > Unfortunately when I do, I get this error message: > > No such polymorphic_identity 'smtp' is defined > > I was hoping SQLA would understand this and let me pack the two > objects into the same table, but for some reason it doesn't like it. > > If someone could please give me some pointers on how to proceed, it > would be greatly appreciated. Thank you in advance for your time and > consideration.
the pattern you're attempting here is called "single table inheritance". You will need to define a common base class between your two classes, but it never need be instantiated directly. Full documentation on how to use this approach is at http://www.sqlalchemy.org/docs/05/mappers.html#single-table-inheritance . > > Kind regards, > moggie. > > -- > > 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.
