tablepersubclass

tablepersubclass is a mapping strategy in object-relational mapping (ORM) that is used to store the data for a class hierarchy in a relational database. In this approach, each concrete subclass of a mapped superclass is assigned its own separate table. The table for a subclass typically contains all the columns corresponding to the fields of that subclass, including those inherited from its superclass. This means that data for a subclass is fully contained within its own table, and no joins are generally required to retrieve an instance of a subclass.

This strategy can offer performance advantages when querying specific subclasses, as it avoids the need to join tables and filter based on a type discriminator column, which is common in other ORM mapping strategies like single table inheritance. However, it can lead to a proliferation of tables, especially in deep inheritance hierarchies. The primary key of each subclass table is usually a foreign key referencing the primary key of its superclass table, though this is not strictly required and depends on the ORM's implementation. The superclass itself might not have a table in the database, or it might have a table that only contains common fields if it's not abstract.