django-timestampable 1.1.4

Timestamps and Soft Delete Patterns in Django Models

Django Timestamps

Timestamps and Soft Delete Patterns in Django Models.

How to install

Option a)

$ pip install django-timestampable

Option b)

To install django-timestampable with Django Rest Framework included:

$ pip install "django-timestampable[drf]"

You can use the first option if you have Django Rest Framework already installed.

 

And add "timestamps" to your INSTALLED_APPS settings

INSTALLED_APPS = [
    # ...
    'timestamps',
]

Or, if you installed with Django Rest Framework:

INSTALLED_APPS = [
    # ...
    'rest_framework',
    'timestamps',
]

Usage

a) For models you want timestamps, just inherit Timestampable:

from timestamps.models import models, Timestampable


class YourModel(Timestampable):
    # your fields here ...

b) For models you want soft-delete, just inherit SoftDeletes:

from timestamps.models import models, SoftDeletes


class YourModel(SoftDeletes):
    # your fields here ...

c) If you want both, you can also inherit from Model for shorter convenience:

# to this:
from timestamps.models import models, Model  # explicit import Model (which contains timestamps)

# instead of:
# from django.db import models

# Explicitly import of "Model" is required
# because models.Model is the original from Django models module


class YourModel(Model):
    # your fields here ...

Soft Deleting

• To get all objects without the deleted ones:

queryset = YourModel.objects

• To get only deleted objects:

queryset = YourModel.objects_deleted

• To get all the objects, including deleted ones:

queryset = YourModel.objects_with_deleted

To soft delete an instance

some_model = MyModel.objects.first()
some_model.delete()  # or some_model.delete(hard=False)

To restore an instance

some_model = MyModel.objects_deleted.first()
some_model.restore()

To hard delete an instance

some_model = MyModel.objects.first()
some_model.delete(hard=True)

To bulk soft delete a queryset

qs = MyModel.objects  # you can also apply filters to bulk delete a subset: qs = MyModel.objects.filter(...)
qs.delete()  # or qs.delete(hard=False)

To bulk hard delete a queryset

qs = MyModel.objects  # ... bulk hard delete a subset: qs = MyModel.objects.filter(...)
qs.delete(hard=True)

To bulk restore a queryset

qs = MyModel.objects_deleted  # ... bulk restore a subset: qs = MyModel.objects_deleted.filter(...)
qs.restore()  # or qs.delete(hard=False)

 

---

 

Signals for Soft Deleting and Restoring

You have 4 signals available that you can listen in your project:

• pre_soft_delete
• post_soft_delete
• pre_restore
• post_restore

To use them, just import the signals and register listeners for them. Eg:

Pre Soft Delete

from timestamps.signals import pre_soft_delete
from django.dispatch import receiver

@receiver(pre_soft_delete)
def on_pre_soft_delete(sender, instance, **kwargs):
    print(f"Model {sender} with id {instance.pk} will be deleted!")

Post Soft Delete

from timestamps.signals import post_soft_delete
from django.dispatch import receiver

@receiver(post_soft_delete)
def on_post_soft_delete(sender, instance, **kwargs):
    print(f"Model {sender} with id {instance.pk} was deleted at {instance.deleted_at}!")

Pre Restore

from timestamps.signals import pre_restore
from django.dispatch import receiver

@receiver(pre_restore)
def on_pre_restore(sender, instance, **kwargs):
    print(f"Model {sender} with id {instance.pk} deleted at {instance.deleted_at} will be restored!")

Post Restore

from timestamps.signals import post_restore
from django.dispatch import receiver

@receiver(post_restore)
def on_post_restore(sender, instance, **kwargs):
    print(f"Model {sender} with id {instance.pk} restored!")

 

---

 

If you're using DRF

You can use the SoftDeleteModelViewSet along with DefaultRouter present in this package and you will have access to a complete CRUD on soft deleted objects as well. This 2 classes allows you to expose:

Consider a Dummy Model that inherits from SoftDelete.

You can have all routes for CRUD operations on this model:

VERB	URL PATH	DESCRIPTION
GET	/dummy/	gets all the objects, without the deleted ones
POST	/dummy/	creates a new object
DELETE	/dummy/[?permanent=<true,false>]	deletes all objects (or a filtered subject). allows hard-delete. Default: soft-delete
GET	/dummy/<pk>/	gets a non-deleted object (by primary key)
POST	/dummy/<pk>/	updates an object (by primary key)
PATCH	/dummy/<pk>/	partial updates an object (by primary key)
DELETE	/dummy/<pk>/[?permanent=<true,false>]	deletes a non-deleted object (by primary key)
PATCH	/dummy/restore/	restore all objects (or a filtered subject)
PATCH	/dummy/<pk>/restore/	restores a soft-deleted object (by primary key)
GET	/dummy/deleted/	gets all deleted objects
GET	/dummy/deleted/<pk>/	gets a deleted object (by primary key)
GET	/dummy/with-deleted/	get all objects, deleted included
GET	/dummy/with-deleted/<pk>/	get an object (by primary key)

 

The query parameter "permanent" it's case-sensitive and can also be one of the values:

truthful_options = [
    't', 'T',
    'y', 'Y', 'yes', 'Yes', 'YES',
    'true', 'True', 'TRUE',
    'on', 'On', 'ON',
    '1', 1,
    True
]

falsely_options = [
    'f', 'F',
    'n', 'N', 'no', 'No', 'NO',
    'false', 'False', 'FALSE',
    'off', 'Off', 'OFF',
    '0', 0,
    'null',
    False
]

How to expose all CRUD operations

# dummy/views.py
from timestamps.drf import viewsets  # instead of: from rest_framework import viewsets
from .models import Dummy
from .serializers import DummySerializer


class DummyModelViewSet(viewsets.ModelViewSet):
    queryset = Dummy.objects.all()
    serializer_class = DummySerializer

# dummy/urls.py
from timestamps.drf import routers  # instead of: from rest_framework import routers
from .views import DummyModelViewSet


router = routers.DefaultRouter()
router.register(r'dummy', DummyModelViewSet)


urlpatterns = router.urls

Note A

For security reasons, by default, if you pass to the query parameter "?permanent=true" on a bulk destroy, the view will not let you hard-delete, raising a PermissionDenied. If you want to enable it on your project, just add to the project settings:

TIMESTAMPS__BULK_HARD_DELETE = True

It's here to prevent users of "forgetting" that the routes also expose bulk hard-delete by default. In production, you can set this flag to True and manage hard-deleting using DRF permissions.

Hard-deleting one object at time is allowed by default.

 

NOTE B

Bulk actions of restoring and deleting returns no content (status code 204) by default. If you want to return a response with the number of deleted/restored objects, just add this setting:

TIMESTAMPS__BULK_RESPONSE_CONTENT = True

Example of returned response: {"count": 3 }

 

Note C

If you don't want to expose all the crud operations, be free to register as:

router.register(r'dummy', DummyModelViewSet.as_view({'get': 'list_with_deleted'}))  # e.g.

And you can always use the mixins instead and create your APIViews:

from rest_framework import generic
from timestamps.drf.mixins import ListDeletedModelMixin
from .models import Dummy
from .serializers import DummySerializer

class MyView(ListDeletedModelMixin, generic.GenericAPIView):
    queryset = Dummy.objects.all()
    serializer_class = DummySerializer
    
    def list_deleted(self, request, *args, **kwargs):
        # optional. your code goes here...

Internally, the ListDeletedModelMixin just calls the method ListModelMixin.list(self, request, *args, **kwargs). The method of determining if the queryset must get all objects, only the deleted or all with deleted is done using AOP, which means that the method GenericAPIView.get_queryset() is advised at runtime to map the current action to the correct queryset the view needs.

If you don't inherit from generic.GenericAPIView, you must be aware that, for this type of scenarios, you need to override the method get_queryset() to return the objects that matches your needs.