I have a one to one relationship between Company and Employee where Employee is subclassed using joined table inheritance into Manager and Engineer. I'm trying to query for a list of companies with the employee eagerloaded including the type-specific columns.
I've been looking at the example at http://www.sqlalchemy.org/docs/mappers.html#creating-joins-to-specific-subtypes, but I can't figure out how to construct a query to eagerload the attributes onto the employee on the company. Here's what I have at the moment: companies = Session.query(Company) \ .join(( Employee.__table__ \ .outerjoin(Engineer.__table__) \ .outerjoin(Manager.__table__), Company.employee )) \ .all() which generates SELECT <company columns> FROM companies INNER JOIN ( SELECT <employee columns>, <engineer columns>, <manager columns> FROM employees LEFT OUTER JOIN engineers ON employees.id = engineers.id LEFT OUTER JOIN managers ON employees.id = managers.id ) AS anon_1 ON anon_1.employees_id = companies.employee_id So I guess I need to get the Engineer and Manager columns into the field list and then for them to be populated on the Company.employee relationship - I'm struggling with this. Is there such as thing as with_polymorphic() for joinedload()? My next question is about how to manage this sort of query strategy in the long term when the total number of subtypes might get larger (e.g. 50 types of employees). The number of types per company would remain low (e.g. a TechCompany might have Engineers and Managers, but not Designers or Salesmen). Should I somehow store the types of employee to query polymorphically for on a per-Company basis? -- 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.
