Updating Model of Existing Database

[autumn viper]

Greetings. How does one update a model without the need to delete existing data?

[tight cosmos]

What kind of update do you need to do? Add fields, modify fields? Something else?

At a very high level. It's running makemigrations, the migrate

[autumn viper]

I was to add a uuid column to become the new primary key.

*want

[tight cosmos]

I wouldn't recommend that (changing the PK to a uuid)
I would recommend adding the uuid field with unique set to True which will achieve a similar thing with less pain.

[autumn viper]

Okay cool. Why do you advise against it?

[tight cosmos]

It means you would need to update everything related model that is linked via a Foreign Key and Many2Many Fields. Not to mention the broad assumption that PKs are integers in various places within Django. Also doing such a migration effectively means you need to create a whole new table, migrate the data, then drop the old one.

Where as adding a field is much simpler migration process.

1. Add the field with null=True, unique=True
2. Create an empty migration and add code to populate existing rows with UUIDs
3. Add a final migration to change null=False to ensure uuids are unique going forward.

[autumn viper]

Ah I see. Many thanks, kind stranger 😃

[tight cosmos]

Your welcome 🙂