django loaddata fails because of concurrent database query - django

Question

I am trying to migrate the database of one my django projects from sqlite to mysql. I first dumped the whole thing with ./manage.py dumpdata > dump.json and prepared the database with ./manage.py migrate and deleted any created data in the tables (This was necessary, as the dump holds all the data).
When I wanted to import the data into the new database with ./manage.py loaddata, there were a lot of errors I was able to resolve, but I can't find the source of this error:
Processed 330984 object(s).Traceback (most recent call last):
File "/app/manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.5/site-packages/django/core/management/__init__.py", line 363, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.5/site-packages/django/core/management/__init__.py", line 355, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python3.5/site-packages/django/core/management/base.py", line 283, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.5/site-packages/django/core/management/base.py", line 330, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python3.5/site-packages/django/core/management/commands/loaddata.py", line 69, in handle
self.loaddata(fixture_labels)
File "/usr/local/lib/python3.5/site-packages/django/core/management/commands/loaddata.py", line 109, in loaddata
self.load_label(fixture_label)
File "/usr/local/lib/python3.5/site-packages/django/core/management/commands/loaddata.py", line 175, in load_label
obj.save(using=self.using)
File "/usr/local/lib/python3.5/site-packages/django/core/serializers/base.py", line 205, in save
models.Model.save_base(self.object, using=using, raw=True, **kwargs)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 837, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 904, in _save_table
forced_update)
File "/usr/local/lib/python3.5/site-packages/django/db/models/base.py", line 954, in _do_update
return filtered._update(values) > 0
File "/usr/local/lib/python3.5/site-packages/django/db/models/query.py", line 664, in _update
return query.get_compiler(self.db).execute_sql(CURSOR)
File "/usr/local/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 1199, in execute_sql
cursor = super(SQLUpdateCompiler, self).execute_sql(result_type)
File "/usr/local/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 894, in execute_sql
raise original_exception
File "/usr/local/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 884, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.5/site-packages/django/db/backends/utils.py", line 60, in execute
self.db.validate_no_broken_transaction()
File "/usr/local/lib/python3.5/site-packages/django/db/backends/base/base.py", line 448, in validate_no_broken_transaction
"An error occurred in the current transaction. You can't "
django.db.transaction.TransactionManagementError: Problem installing fixture '/path/to/django/dump.json': Could not load auth.User(pk=1): An error occurred in the current transaction. You can't execute queries until the end of the 'atomic' block.
I already tried to remove all signal receivers, so that none of my own code is run when executing loaddata.
Has anyone else experienced similar behaviour with django's loaddata and managed to get it working?
Context:
python v3.5
django v1.11.4
only stdlib django model fields used

Answer 1

This is more of a workaround than a solution, but it did solve my problem.
After further investigation I realized that the auth.user model somehow triggered the query and broke the import.
The solution was to write a simple script to split the dump into multiple parts (I did not have access to the database anymore) and then import them in the correct order: contenttypes, auth, and the rest.
You can find the script here.
This is how I split up the dump:
./investigate-django-dump.py dump.json extract contenttypes. > contenttypes.json
./investigate-django-dump.py dump.json extract auth. > auth.json
./investigate-django-dump.py dump.json extractnot auth.,contenttypes. > data.json