Wagtail migration doesn't respect --run-syncdb

Running migrate under wagtail creates tables with data despite using --run-syncdb. As a result of this, it is difficult to load a database dump via ./manage.py loaddata. It fails because some tables are not empty. There are open tickets where people come up with unnecessary complicated hacks to load data:

• https://github.com/wagtail/wagtail/issues/4472
• https://github.com/wagtail/wagtail/issues/5464

This would all become quite simple if the wagtail migration would respect --run-syncdb

Issue Summary

When running ./manage.py migrate --run-syncdb, some wagtail tables are initialized with data which they should not. At least the following tables are not empty:

• " wagtailcore_page"
• " wagtailcore_site"
• " wagtailcore_groupcollectionpermission"
• " wagtailcore_grouppagepermission"

Steps to Reproduce

1. Start a new project with wagtail start myproject
2. Run ./manage.py migrate --run-syncsb
3. Inspect tables listed above

Expected Behaviour

When running migrations with --run-syncdb on an empty database, empty tables should be created without any data

Technical details

• Python version: 3.7.5
• Django version: 3.0.4
• Wagtail version: 2.8

[gasman]

./manage.py migrate followed by ./manage.py flush should give you an empty database with all tables intact.

[eeintech]

@gasman On my side I am trying to migrate from SQLite3 to a PostgreSQL database, so I followed this guide: https://gist.github.com/sirodoht/f598d14e9644e2d3909629a41e3522ad

It does say to run it with --run-syncdb option, which in my mind is the way to create empty tables which will be filled up with the loaddata command later on.

I ran into a separate issue (I believe related to #6069) but after configuring my PostgreSQL database as default in my base.py Django settings file, I ran into another error:

Traceback (most recent call last):
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/django/db/backends/utils.py", line 86, in _execute
    return self.cursor.execute(sql, params)
psycopg2.errors.UniqueViolation: duplicate key value violates unique constraint "wagtailcore_page_path_key"
DETAIL:  Key (path)=(00010001) already exists.


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "./manage.py", line 20, in <module>
    execute_from_command_line(sys.argv)

(...troncated ...)

django.db.utils.IntegrityError: Problem installing fixture '/home/eeintech/eeintech/datadump.json': Could not load wagtailcore.Page(pk=7): duplicate key value violates unique constraint "wagtailcore_page_path_key"
DETAIL:  Key (path)=(00010001) already exists.

Indeed:

>>> from wagtail.core.models import Page
>>> Page.objects.all()
<PageQuerySet [<Page: Root>, <Page: Welcome to your new Wagtail site!>]>

I deleted the Page instance but still running into a content type error when running loaddata:

django.db.utils.IntegrityError: Problem installing fixture '/home/eeintech/eeintech/datadump_content.json': Could not load contenttypes.ContentType(pk=16): duplicate key value violates unique constraint "django_content_type_app_label_model_76bd3d3b_uniq"
DETAIL:  Key (app_label, model)=(wagtailsearch, query) already exists.

And can’t find a way to delete the initial content load from the shell:

>>> ContentType.objects.all().delete()
Traceback (most recent call last):
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/django/db/backends/base/base.py", line 243, in _commit
    return self.connection.commit()
psycopg2.errors.ForeignKeyViolation: update or delete on table "django_content_type" violates foreign key constraint "wagtailcore_page_content_type_id_c28424df_fk_django_co" on table "wagtailcore_page"
DETAIL:  Key (id)=(1) is still referenced from table "wagtailcore_page".

So I’ve tried to dump the data exluding content types python manage.py dumpdata --exclude=contenttypes --exclude=auth.Permission > dumpdata_nocontent.json as a workaround (suggested here) but no luck:

$ ./manage.py loaddata datadump_nocontent.json
Traceback (most recent call last):
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/django/contrib/contenttypes/models.py", line 110, in get_for_id
    ct = self._cache[self.db][id]
KeyError: 64

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/wagtail/core/models.py", line 936, in get_indexed_instance
    return self.specific
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/django/utils/functional.py", line 48, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/wagtail/core/models.py", line 620, in specific
    content_type = ContentType.objects.get_for_id(self.content_type_id)
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/django/contrib/contenttypes/models.py", line 114, in get_for_id
    ct = self.get(pk=id)
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/django/db/models/manager.py", line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/eeintech/virtualenv/eeintech/3.7/lib/python3.7/site-packages/django/db/models/query.py", line 417, in get
    self.model._meta.object_name
django.contrib.contenttypes.models.DoesNotExist: ContentType matching query does not exist.

Anyway, I digress…

What’s your proposed way to be able to create tables but not load initial data? Better yet, what your proposed way for migrating data from one database to another?

Thanks a lot.