CODEWITHSUNDEEP
djangodjango-models
jidicula
jidicula

Reputation: 3989

Create a Django fixture file that leaves some fields unchanged when loaded into DB

Is it possible to create a fixture that is written to the DB using loaddata, and overwrites some fields of an existing record, but not all of them?

For example, suppose I have a table in my DB called app_foo:

id bar baz
1 "a" "b"
2 "c" "d"

The corresponding YAML fixture file for this would look like:

- model: app.foo
  pk: 1
  fields:
    bar: "a"
    baz: "b"
- model: app.foo
  pk: 2
  fields:
    bar: "c"
    baz: "d"

How would I modify this fixture such that:

  1. Records 1 and 2 have an empty baz field when loading the fixture into a fresh empty database.
  2. When the fixture is loaded into a database already containing records 1 and 2 that have values for baz, they aren't overwritten with NULL.

I thought that I could do something like this:

- model: app.foo
  pk: 1
  fields:
    bar: "a"
- model: app.foo
  pk: 2
  fields:
    bar: "c"

or this:

- model: app.foo
  pk: 1
  fields:
    bar: "a"
    baz:
- model: app.foo
  pk: 2
  fields:
    bar: "c"
    baz:

But both attempts overwrote the baz field for DB records 1 and 2 with NULL. This isn't specified in the documentation for fixtures, but is an empty field in a fixture implicitly NULL?

Upvotes: 0

Views: 524

Answers (1)

iklinac
iklinac

Reputation: 15758

As written in documentation you linked

Each time you run loaddata, the data will be read from the fixture and re-loaded into the database. Note this means that if you change one of the rows created by a fixture and then run loaddata again, you’ll wipe out any changes you’ve made.

Django does not set values for fields that are not in fixture but they default to default field value, which is NULL in case you set null=true

Upvotes: 2

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