#24632: PostgreSQL table inheritance
-------------------------------------+-------------------------------------
Reporter: yennicks | Owner:
Type: New feature | Status: new
Component: contrib.postgres | Version: master
Severity: Normal | Resolution:
Keywords: orm postgresql | Triage Stage: Accepted
table-inheritance inheritance |
object-relational |
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by charettes):
I think it might be worth exploring a way to specify how model inheritance
should be handled at the database level.
This could allow us to support MTI (the actual), STI (Single Table
Inheritance) and PostgreSQL table inheritance.
IMHO it would be more worthwhile to abstract this whole concept with
documented caveats and limitations because it's going to be hard to mimic
the actual MTI implementation (Fk's as primary keys) with PostgreSQL table
inheritance.
For example, constraints are not inherited by children tables so the
following scenario would fail if we simply replaced the existing MTI model
on PostgreSQL by table inheritance.
{{{#!python
class Parent(models.Model):
pass
class Child(Parent):
pass
class Referent(models.Model):
parent = models.ForeignKey(Parent)
}}}
{{{#!sql
CREATE TABLE parent (id serial PRIMARY KEY);
CREATE TABLE child () INHERITS (parent);
CREATE TABLE referent (
parent_id int REFERENCES parent
);
}}}
{{{#!python
>>> child = Child.objects.create()
>>> ref = ParentReferent(parent=child)
IntegrityError ...
}}}
{{{#!sql
ERROR: insert or update on table "referent" violates foreign key
constraint "referent_parent_id_fkey"
DETAIL: Key (parent_id)=(1) is not present in table "parent".
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/24632#comment:2>
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