Re: Corrupted Migration?

> I have tried that (by the way, the offending migration didn't show up in the django_migrations table because the migration failed).
>
> I think we might be talking past each other. Sorry if I'm being unclear. Here's an example of what's going on:
> Before migration, my database is at state X, and my migrations files reflect that.
> I change my model file, updating the state (let's call it state Y). Then, I run make migrations, generating a new migration file that corresponds to state Y.
> I run the migrate command to get my database to state Y. It fails, so now my database is back at state X. There is nothing in the database to delete (not even from the django_migrations table) because the transaction was rolled back.
> I delete the migration file that corresponds to state Y. My database is back in state X, and my migration files again reflect that.
> I run the migrate command again, and it fails (same problem). The error is django.db.models.fields.FieldDoesNotExist: [Model] has no field named [field].

After you delete Y migration, have you searched your migration files to verify that there are no references to that field?

> [field] corresponds to a new field in state Y, not in an existing field in state X. I'm confused - why is it looking for a field that doesn't exist in the pre-migrated state (state X)?

Do you have any RunPython or other custom modifications in your migrations that would cause an object based on your modified model to be created (and saved), possibly relying on a default value for the new 'field' specified in your Y-version model, maybe as part of a data migration?

> So, I assume that the model state somehow is de-synced from the database/migration state. I hop into the Django shell and check the model metadata. The fields exactly match state Y. My database is still in state X.
> Does that make sense?

Makes perfect sense when you think about it. Being out of sync in this manner happens constantly, and is exactly why migrations exist.

Django makes the assumption that the current values in your models.py files exactly match the layout of the DB, since you should be syncing everything using migrations and validating via tests.

Any time you modify a model, the DB and you model definitions become out of sync, with your models being 'ahead' of your DB since you haven't informed the DB of your model changes via migrations yet.

Think of it like someone writing you a check. Your relative personal wealth increases as soon as you receive the check, but your bank statement won't agree with you until you submit the check to them so that they can credit your account accordingly.

Feel free to write me a check (for a large amount, bigger the better) so I can demonstrate the effect it has on my bank account. ;-)

-James

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/CA%2Be%2BciXbv9YVy_AZG0uaVhG%3D6w8HYosuU4tGRnSwYDxeyARwkA%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.