django-reversion undo功能 - 恢复多个对象

Question

I'm trying to implement 'undo' feature in django project with django-reversion in a case when user can accidentally modify multiple objects. Using admin panel won't work as one has to revert objects one-by-one.

My problem is that I am unable to create revision that holds data about more than one object.
Even when I do

with reversion.create_revision():
    Res.object.all().delete()

then I cannot access revision that groups this change. It's splitted in a "one object one revision.models.Version" manner.

In [103]: reversion.models.Version.objects.all()
Out[103]: [<Version: #00001>, <Version: #00002>]

I've tried also through

reversion.models.Revision.objects.all().order_by('-date_created')[0].version_set.all()

but it also returned only one Version for one deleted Res object. Seems like I'm missing something.

Answer 1

tl;dr - A revision isn't something you 'undo'. It's something you restore. Thus, undoing is a case of finding the most recent revision that occurred before the thing you want to undo, and restore it by calling revert().

The data model for django-reversion is based around Revisions and Versions. A Revision consists of one or more Versions, and a Version represents the serialized state of one Django model.

django-reversion allows you to roll back to the state of any previous Version or Revision. This is similar to, but not identical to an undo functionality.

Consider the following workflow:

# Create a Revision containing two Versions.
with reversion.create_revision():
    a = SomeModel.objects.create(name="A version 1")
    b = SomeModel.objects.create(name="B version 1")

# Create a Revision containing to Versions.
with reversion.create_revision():
    a.name = "A version 2"
    a.save()
    b.name = "B version 2"
    b.save()

At this point, you can 'undo' the second edit by reverting to the last revision.

# Revert just 'a' to version 1. This is the last but one revision.
reversion.get_for_object(a)[1].revert()

# Or, revert 'a' and 'b' to version 1.
reversion.get_for_object(b)[1].revision.revert()

You can also delete and recover like so:

# Store the pk of 'a', then delete it.
a_pk = a.pk
a.delete()

# Recover 'a' via it's primary key.
reversion.get_deleted(SomeModel).filter(object_id=a_pk).revert()

So you can revert to a previous state of a single model, or a group of models saved together. However, there is no way to say 'undo what I just did'. Instead, you have to tell reversion 'become like you were at this time'.

In your case, if you wanted to undo a bulk delete, you could do it like this:

# Save a revision containing all SomeModel instances.
with reversion.create_revision():
    for obj in SomeModel.objects.all():
        obj.save()

# Delete them all.
SomeModel.objects.delete()

# Revert back to the previous revision, where nothing was deleted.
Revision.objects.filter(version__content_type=ContentType.objects.get_for_model(SomeModel)).order_by("-date_created")[0].revert()

In this case, however, you'll get a very silly race condition, since other revisions for SomeModel could be created at any time.

Answer 2

I finally got it.

Issue 1: Store changes related to multiple objects in a single Revision

Solution: add TransactionMiddleware to MIDDLEWARE_CLASSES

Issue 2: Undo feature / reverting changes

Well, this is confusing. You cannot REVERT CHANGES you can RESTORE OBJECT to previously known state. And using reversion.create_revision() in your object-altering views stores data about that object after changing it . If you have view that modify multiple object then you have to create revision before making actual changes.

This is also visible in admin panel. If you change your object than a new log entry will appear. But if you want to revert that change than you cannot select newest version -- it is identical with the current state of the object -- instead you have to choose the previous one.