Single Table Inheritance in Django

python django django-models single-table-inheritance
sutee picture sutee · Oct 27, 2008 · Viewed 12.5k times · Source

Is there explicit support for Single Table Inheritance in Django? Last I heard, the feature was still under development and debate.

Are there libraries/hacks I can use in the meantime to capture the basic behavior? I have a hierarchy that mixes different objects. The canonical example of a corporation structure with an Employee class, subclasses for types of employees, and a manager_id (parent_id) would be a good approximation of the problem I am solving.

In my case, I would like to represent the idea that an employee can manage other employees while being managed by a different employee. There are not separate classes for Manager and Worker, which makes this hard to spread across tables. Sub-classes would represent types of employees-programmers, accountants, sales, etc and would be independent of who supervises who (OK, I guess it's no longer a typical corporation in some respect).

Answer

Björn Lindqvist picture Björn Lindqvist · Nov 12, 2009

I think the OP is asking about Single-Table Inheritance as defined here:

Relational databases don't support inheritance, so when mapping from objects to databases we have to consider how to represent our nice inheritance structures in relational tables. When mapping to a relational database, we try to minimize the joins that can quickly mount up when processing an inheritance structure in multiple tables. Single Table Inheritance maps all fields of all classes of an inheritance structure into a single table.

That is, a single database table for a whole hierarchy of entity classes. Django does not support that kind of inheritance.

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