I have the following situation:
It would be simple enough but I encountered a problem with the data migration. It sends a query for a specific ContentType which I need for django-taggit. The problem is that the model I want to query didn't exist until the migration that preceded it. That errors out with an empty result from that query.
However, when I run all migrations up to the data migration and then I run the data migration itself, everything works well. I've noticed that a migration process doesn't save changes until all of the migrations are finished which doesn't work for this.
One of the solutions I got to was to manually commit/save changes to the database however I haven't been able to find a way to do it. Of course, if there are any other ideas/better solution I'd be happy to hear them.
This is the code where the data migration errors out:
# ChallengeContest ContentType
challenge_contest_ct = ContentType.objects.get(model='challengecontest')
As you can see the model challengecontest is the one that was created in a migration preceeding data migration.
I have found data migrations to be more trouble than they're worth. In my last two jobs we abandoned them, replacing them with writing one-off management commands.