Queries regarding Custom Managers with model inheritance.

[Dheerendra Rathor]

I was going through https://docs.djangoproject.com/en/1.9/topics/db/managers/#custom-managers-and-model-inheritance regarding custom managers and I decided to do some tests. Here are my models:

from django.db import models

class CustomManager(models.Manager):

    use_for_related_fields = True

class ExtraManager(models.Manager):

    use_for_related_fields = True

class AnotherManager(models.Manager):

    use_for_related_fields = True

class A(models.Model):

    objects = CustomManager()

    all_objects = AnotherManager()

    class Meta:

        abstract = True

class B(A):

    pass

class C(A):

    objects = ExtraManager()

class D(C):

    pass

class E(A):

    all_objects = AnotherManager()

    objects = ExtraManager()

class F(E):

    pass

Here are the results of few code executions:

In [1]: from app.models import *

In [2]: F.objects

Out[2]: <django.db.models.manager.Manager at 0x7f160dfe8e48>

In [3]: D.objects

Out[3]: <app.models.ExtraManager at 0x7f160dfe80b8>

In [4]: D._default_manager

Out[4]: <app.models.AnotherManager at 0x7f160dfe8978>

In [5]: F._de

F._default_manager  F._deferred         

In [5]: F._default_manager

Out[5]: <django.db.models.manager.Manager at 0x7f160dfe8e48>

In [6]: F.all_objects

Out[6]: <app.models.AnotherManager at 0x7f160dfe87f0>

Here I have few queries:

- How come AnotherManager is default Manage for D? It is neither default manager for C and neither it is first Manager in A.

 

- Why D.objects is ExtraManager (from C objects) but F.objects is default Django Manager

Someone please help to understand theses. Thanks!