Thanks for your replies Markus! I've added a ticket here https://code.djangoproject.com/ticket/24016
On Wednesday, December 17, 2014 10:47:26 AM UTC-5, Markus Holtermann wrote: > > I agree, a general "here's how you should do it" section in the docs > should be added. Would you mind opening a ticket on > https://code.djangoproject.com/ where you state the problem (e.g. link to > this discussion). Thanks. > > /Markus > > On Wednesday, December 17, 2014 6:01:05 AM UTC+1, John-Scott wrote: >> >> My 'solution' was very smelly: >> >> - created the migration in 'my_app' as mentioned in my previous post >> - pushed this change to production to run >> - removed 'foo_tag' from INSTALLED_APPS *AND* deleted the migration >> file (which meant also manually deleting the history of this migration >> from >> the django_migrations table). >> >> It was hard to hold my nose through this experience but it worked. Would >> be great to have a general solution that could be shared with others but in >> the meantime, I'll settle for being able to get on with the rest of my life. >> >> On Tuesday, December 16, 2014 9:05:35 AM UTC-5, Markus Holtermann wrote: >>> >>> Hey John-Scott, >>> >>> I'm afraid but I don't see an obvious solution. There are 2 ways you >>> could work on the issue, I don't like either: >>> >>> 1. remove all references to the "foo_tag" app from all migration files >>> >>> 2. make use of the MIGRATION_MODULES settings: >>> >>> 2.1. create a package "path.to.foo_tag_legacy" >>> 2.2. inside create an empty migration "0001_initial" >>> 2.3. define MIGRATION_MODULES={"foo_tag": "path.to.foo_tag_legacy"} >>> >>> As said, both seem ugly to me. I don't know which way I'd proceed. >>> >>> You might get it working by squashing migrations, but certainly not >>> without manually writing those migration files. >>> >>> /Markus >>> >>> On Saturday, December 13, 2014 6:26:17 PM UTC+1, John-Scott wrote: >>>> >>>> Say I decided to switch from a third party app foo-tags to app >>>> bar-tags. Their Tag models are mostly identical so I just need to move the >>>> data from foo-tag to bar-tag. Since I don't control their migrations, I'd >>>> need to create a migration in one of my own apps: >>>> >>>> ./manage.py makemigrations my_app --empty >>>> >>>> In this migration I'd need to explicitly list the dependencies on these >>>> external apps (otherwise was getting errors that the foo and bar apps were >>>> not available in the app registry): >>>> >>>> # -*- coding: utf-8 -*- >>>> from __future__ import unicode_literals >>>> >>>> from django.db import models, migrations >>>> >>>> def migrate_tags(apps, schema_editor): >>>> FooTag = apps.get_model('foo_tag', 'FooTag') >>>> BarTag = apps.get_model('bar_tag', 'BarTag') >>>> for old_tag in FooTag.objects.all(): >>>> new_tag = BarTag.objects.create(name=old_tag.name) >>>> >>>> class Migration(migrations.Migration): >>>> dependencies = [ >>>> ('my_app', '0001_initial'), >>>> ('foo_tag', '0001_initial'), >>>> ('bar_tag', '0001_initial'), >>>> ] >>>> >>>> operations = [ >>>> migrations.RunPython(migrate_tags) >>>> ] >>>> >>>> >>>> The migration itself works as expected. However if I now remove foo_tag >>>> from INSTALLED_APPS, Django will now give an error: >>>> >>>> KeyError: "Migration my_app.0002_auto_20141212_1951 dependencies >>>> reference nonexistent parent node ('foo_tag', '0001_initial')" >>>> >>>> What's the correct way to handle migrating data between 3rd party apps >>>> where one of the apps is eventually removed? >>>> >>>> Thanks, >>>> John-Scott >>>> >>> -- 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 [email protected]. To post to this group, send email to [email protected]. 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/9ac3c6c9-b36b-450a-9527-687623c1165c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
