Django multi-table inheritance with separate (identical) tables without pointers

Question

I'm subclassing an existing model (from another application entirely) and want my model to have its own database table. An identical clone/replica of the original table, not just a table with a pointer to the data stored in the "parent" table.

Here's my model:

class A (models.Model):
    name = models.CharField('name')

class MyA (A):
    class Meta:
        db_table = 'My_A'

Here's my DB tables:

CREATE TABLE A
(
  id serial NOT NULL,
  "name" character varying(50) NOT NULL,
  ...
)

CREATE TABLE My_A
(
  A_ptr_id integer NOT NULL,
  ...
)

And here's what I would like to have:

CREATE TABLE A
(
  id serial NOT NULL,
  "name" character varying(50) NOT NULL,
  ...
)

CREATE TABLE My_A
(
  id serial NOT NULL,
  "name" character varying(50) NOT NULL,
  ...
)

Edit: I ended up copy-pasting the 3rd party model

None really. Model A is imported from another application (also used for it's primary purpose in my project) and I want to separate the stored data. — Pala
– Pala, Commented Aug 22, 2012 at 8:54

Benargee · Accepted Answer · 2019-06-12 01:36:08Z

4

If I am understanding you correctly, you can create an abstract base class that won't have its own table. From there you could then create multiple classes that inherit from that base class that have their own tables.

class ABase(models.Model):
    name = models.CharField('name')
    class Meta:
        abstract = True

class A(ABase):
    class Meta:
        db_table = 'A'

class MyA(ABase):
    class Meta:
        db_table = 'My_A'

Django 2.2 Documentation - Abstract base classes

answered Jun 12, 2019 at 1:36

Benargee

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Comments

schacki · Accepted Answer · 2012-08-22 09:13:34Z

0

New approach (if you insist on separating the data): create model MyA without inheriting from A and create another model MergeA that creates explicit generic foreign key to My and A. But this will certainly require quite some extra coding.

answered Aug 22, 2012 at 9:13

schacki

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Comments

schacki · Accepted Answer · 2012-08-22 09:10:15Z

-1

When you inherit a Django Model it will always generate an implict 1-1 relation to the parent model. And Django will only generate the fields for your inherited model. Which in general makes total sense to me. But for your use case is cumbersome. Since we are taling about Django core functionality, it might be hard to workaround. You could try to copy and paste your 3rd party model into your code as a proxy model and inherit from there.

Update: But why do you want to separate the data into different tables? What is the final objective?

edited Aug 22, 2012 at 9:10

answered Aug 22, 2012 at 7:33

schacki

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1 Comment

Pala Over a year ago

The 3rd party model(A) is also used for it's primary purpose in my project. And I need to keep them separate so that A.objects.all() only returns the "original" objects. I also would need to run offsite computations to regularly re-populate MyA-table via fixtures (or something) and I don't want to affect the production use of model/table A.

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