Question

I have some base initial data that I want to include in a Django project. It fits perfectly as a fixture except that I might want to reject duplicates. This would mean that I could re-load the data in to an existing installation and it would only add the objects that don’t already exist.

I have used natural keys and foreign keying on the same field, so there are no questions of id clashes etc.

Possible? I don’t want to write a JSON importer when one already exists, and my data is already in a fixture.

Answer 1

Usually fixture contains all the information of a model, which includes the primary key. Here is an example of a fixture from Django site:

[
  {
    "model": "myapp.person",
    "pk": 1,
    "fields": {
      "first_name": "John",
      "last_name": "Lennon"
    }
  },
  {
    "model": "myapp.person",
    "pk": 2,
    "fields": {
      "first_name": "Paul",
      "last_name": "McCartney"
    }
  }
]

As you can see it has a primary key. So even if you have duplicate fixtures, as long as primary keys are the same, whatever is the latest fixture to be imported, that one will overwrite the entries in the db, so you should not have any duplicate data in db.