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    <p>Here is my solution, which fits all of my requirements:</p> <ol> <li>Implement <a href="https://docs.djangoproject.com/en/dev/topics/serialization/#natural-keys" rel="nofollow">natural keys</a> and unique constraints on all models <ul> <li>Allows for a unique way to refer to each object without using primary key IDs</li> </ul></li> <li>Sublcass each model from <a href="https://github.com/django-extensions/django-extensions/blob/master/django_extensions/db/models.py" rel="nofollow">TimeStampedModel</a> in django-extensions <ul> <li>Adds automatically updated <code>created</code> and <code>modified</code> fields</li> </ul></li> <li><p>Create a Django management command for exporting, which filters a subset of data and serializes it with natural keys</p> <pre><code>baz = Baz.objects.filter(foo=bar) yaz = Yaz.objects.filter(foo=bar) objects = [baz, yaz] flat_objects = list(itertools.chain.from_iterable(objects)) data = serializers.serialize("json", flat_objects, indent=3, use_natural_keys=True) print(data) </code></pre></li> <li><p>Create a Django management command for importing, which reads in the serialized file and iterates through the objects as follows: </p> <ul> <li>If the object does not exist in the database (by natural key), create it </li> <li>If the object exists, check the <code>modified</code> timestamps</li> <li>If the imported object is newer, update the fields</li> <li>If the imported object is older, do not update (but print a warning)</li> </ul></li> </ol> <p>Code sample:</p> <pre><code># Open the file with open(args[0]) as data_file: json_str = data_file.read() # Deserialize and iterate for obj in serializers.deserialize("json", json_str, indent=3, use_natural_keys=True): # Get model info model_class = obj.object.__class__ natural_key = obj.object.natural_key() manager = model_class._default_manager # Delete PK value obj.object.pk = None try: # Get the existing object existing_obj = model_class.objects.get_by_natural_key(*natural_key) # Check the timestamps date_existing = existing_obj.modified date_imported = obj.object.modified if date_imported &gt; date_existing: # Update fields for field in obj.object._meta.fields: if field.editable and not field.primary_key: imported_val = getattr(obj.object, field.name) existing_val = getattr(existing_obj, field.name) if existing_val != imported_val: setattr(existing_obj, field.name, imported_val) except ObjectDoesNotExist: obj.save() </code></pre> <p>The workflow for this is to first call <code>python manage.py exportTool &gt; data.json</code>, then on another django instance (or the same), call <code>python manage.py importTool data.json</code>.</p>
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