Reload django object from database

Reload django object from database

Is it possible to refresh the state of a django object from database? I mean behavior roughly equivalent to:
new_self = self.__class__.objects.get(pk=self.pk)
for each field of the record:
    setattr(self, field, getattr(new_self, field))

UPDATE: Found a reopen/wontfix war in the tracker: http://code.djangoproject.com/ticket/901.
Still don't understand why the maintainers don't like this.

Solutions/Answers:

Answer 1:

As of Django 1.8 refreshing objects is built in. Link to docs.

def test_update_result(self):
    obj = MyModel.objects.create(val=1)
    MyModel.objects.filter(pk=obj.pk).update(val=F('val') + 1)
    # At this point obj.val is still 1, but the value in the database
    # was updated to 2. The object's updated value needs to be reloaded
    # from the database.
    obj.refresh_from_db()
    self.assertEqual(obj.val, 2)

Answer 2:

I’ve found it relatively easy to reload the object from the database like so:

x = X.objects.get(id=x.id)

Answer 3:

In reference to @grep’s comment, shouldn’t it be possible to do:

# Put this on your base model (or monkey patch it onto django's Model if that's your thing)
def reload(self):
    new_self = self.__class__.objects.get(pk=self.pk)
    # You may want to clear out the old dict first or perform a selective merge
    self.__dict__.update(new_self.__dict__)

# Use it like this
bar.foo = foo
assert bar.foo.pk is None
foo.save()
foo.reload()
assert bar.foo is foo and bar.foo.pk is not None

Answer 4:

As @Flimm pointed out, this is a really awesome solution:

foo.refresh_from_db()

This reloads all data from the database into the object.

References