Fields deleted on migration

Hello

I just tried an upgrade to django 1.8 form django 1.7.7 and from django-simple-history 1.5.4 to django-simple-history 1.6.1 and run into some problems when running new migrations.

I have several models with ForeignKey fields. After upgrading and running

./manege makemigrations

All the ForeignKey fields got removed and added again, causing data lost.

For instance one migrations does this (tables and fields in spanish):

    ...
    migrations.RemoveField(
        model_name='historicalitemordendecompra',
        name='item_id',
    ),
    ...
    migrations.AddField(
        model_name='historicalitemordendecompra',
        name='item',
        field=models.ForeignKey(null=True, db_constraint=False, blank=True, related_name='+', on_delete=django.db.models.deletion.DO_NOTHING, to='almacen.Item'),
    ),
    ...

I’ve been playing with the idea of manually changing migrations to AlterField and RenameField but that sounds like a lengthy and not sure how safe process.

Help is appreciated.

[jmfederico]

Hello, I did almsot the same as you, but didn’t need to re-run “makemigrations”, I renamed and then altered the fields. I guess the result is the same:

1. Create the autogenerated django migrations (i.e. python manage.py makemigrations)
2. Edit the files: Replace all instances of ‘DeleteField’ with ‘RenameField’ changing name=“x_id” with old_name=“x_id” and adding new_name=“x”
3. Edit the files: Replace all instances of ‘AddField’ to ‘AlterField’
4. Verify that there are no DeleteField instances in the migration files… There shouldn’t be! Voila, all of your data should be good to migrate.
5. Run python manage.py makemigrations to make sure NO new migrations are generated.
6. Migrate the data on a test server (python manage.py migrate). Check to ensure everything’s moved over properly!

Cheers.

[rossmechanic]

Don’t think this issue is relevant anymore.