Swithing ForeignKey in an existing table

Using Django Using the ORM
1

I have a class like this :

class someClass1(models.Model):
    # some field 1
    custom_vhd_azure_tbl = models.ForeignKey(Vhd_azure, on_delete=models.CASCADE)
    # some field n
    created_date = models.DateTimeField(auto_now_add=False, null=True)

I now realize a mistake was made : custom_vhd_azure_tbl should’ve been FKed to Custom_vhd_azure instead.

custom_vhd_azure_tbl = models.ForeignKey(Custom_vhd_azure, on_delete=models.CASCADE)

Some 10 rows of data currently exits in someClass1 table for which it can be truncated.

But what I should do to make the field switch from one FK to another ?

2

Does the Custom_vhd_azure model has any fk to Vhd_azure so you could relate one from the other?
If there’s no relation, then you wont be able to keep the data on these rows

3

Custom_vhd_azure and Vhd_azure are 2 separate distinct tables that have no FKs.

4

Then you have no way of keeping this existing data.
What you can do, if you have a way to, is:

  1. Remove the field custom_vhd_azure_tbl from the model, run makemigrations. It will generate a RemoveField operation
  2. Add the field custom_vhd_azure_tbl in the model for the correct model, run makemigrations. It will generate a AddField operation
  3. Run makemigrations your_app --empty to generate a empty migration, that you can use to write a RunPython operation to populate the existing rows with the proper model for that foreign key.

Following these steps you can “keep” the field custom_vhd_azure_tbl with the new values.

5

How do I execute RunPython post empty makemigrations ?

6

You can find all possible migration operations under this section of the documentation: Migration Operations
And there you can find about RunPython