Django make migrations issue changing to new Postgres DB

Question

I have not been able to find a solution on SO that has worked for me yet, so I figured I would post a question.

I am running into issues migrating a database schema to a new PostgreSQL DB using django.

Here is the connection for my first DB, it works and I am able to run migrations perfectly fine. This is the DB I was using for testing intially, now I want to use a secondary DB and migrate the schema over.

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': '[HOST]',
        'NAME': 'postgres',
        'USER': 'postgres',
        'PASSWORD': '[PW]',
        }
    }

Here is the updated settings:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': '[HOST]',
        'NAME': 'test_mh',       # this is only difference
        'USER': 'postgres',
        'PASSWORD': '[PW]',
        }
    }

I run python3 manage.py makemigrations on the first connection and it is fine.

When I run the same command with the updated DB Name I get exceptions that state my tables do not exist.

  Traceback (most recent call last):
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 85, in _execute
      return self.cursor.execute(sql, params)
  psycopg2.ProgrammingError: relation "objects_community" does not exist
  LINE 1: ...y"."state", "objects_community"."date_added" FROM "objects_c...
                                                               ^


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

  Traceback (most recent call last):
    File "manage.py", line 15, in 
      execute_from_command_line(sys.argv)
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
      utility.execute()
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/__init__.py", line 375, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 316, in run_from_argv
      self.execute(*args, **cmd_options)
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 350, in execute
      self.check()
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 379, in check
      include_deployment_checks=include_deployment_checks,
    File "/usr/local/lib/python3.6/dist-packages/django/core/management/base.py", line 366, in _run_checks
      return checks.run_checks(**kwargs)
    File "/usr/local/lib/python3.6/dist-packages/django/core/checks/registry.py", line 71, in run_checks
      new_errors = check(app_configs=app_configs)
    File "/usr/local/lib/python3.6/dist-packages/django/core/checks/urls.py", line 40, in check_url_namespaces_unique
      all_namespaces = _load_all_namespaces(resolver)
    File "/usr/local/lib/python3.6/dist-packages/django/core/checks/urls.py", line 57, in _load_all_namespaces
      url_patterns = getattr(resolver, 'url_patterns', [])
    File "/usr/local/lib/python3.6/dist-packages/django/utils/functional.py", line 37, in __get__
      res = instance.__dict__[self.name] = self.func(instance)
    File "/usr/local/lib/python3.6/dist-packages/django/urls/resolvers.py", line 533, in url_patterns
      patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
    File "/usr/local/lib/python3.6/dist-packages/django/utils/functional.py", line 37, in __get__
      res = instance.__dict__[self.name] = self.func(instance)
    File "/usr/local/lib/python3.6/dist-packages/django/urls/resolvers.py", line 526, in urlconf_module
      return import_module(self.urlconf_name)
    File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "", line 994, in _gcd_import
    File "", line 971, in _find_and_load
    File "", line 955, in _find_and_load_unlocked
    File "", line 665, in _load_unlocked
    File "", line 678, in exec_module
    File "", line 219, in _call_with_frames_removed
    File "/home/viatech/Projects/ExactEstate/ExactEstate/ExactEstate/urls.py", line 21, in 
      path('adm/', include('interface_admin.urls')),
    File "/usr/local/lib/python3.6/dist-packages/django/urls/conf.py", line 34, in include
      urlconf_module = import_module(urlconf_module)
    File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "", line 994, in _gcd_import
    File "", line 971, in _find_and_load
    File "", line 955, in _find_and_load_unlocked
    File "", line 665, in _load_unlocked
    File "", line 678, in exec_module
    File "", line 219, in _call_with_frames_removed
    File "/home/viatech/Projects/ExactEstate/ExactEstate/interface_admin/urls.py", line 2, in 
      from interface_admin import views
    File "/home/viatech/Projects/ExactEstate/ExactEstate/interface_admin/views.py", line 4, in 
      from forms import RegistrationForm, SQLForm, SingleFileUploadForm, ApartmentTableFormBuilder
    File "/home/viatech/Projects/ExactEstate/ExactEstate/forms/ApartmentTableFormBuilder.py", line 10, in 
      class ApartmentTableFormBuilder(forms.Form):
    File "/home/viatech/Projects/ExactEstate/ExactEstate/forms/ApartmentTableFormBuilder.py", line 16, in ApartmentTableFormBuilder
      for community in Community.objects.all():
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 268, in __iter__
      self._fetch_all()
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 1186, in _fetch_all
      self._result_cache = list(self._iterable_class(self))
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/query.py", line 54, in __iter__
      results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
    File "/usr/local/lib/python3.6/dist-packages/django/db/models/sql/compiler.py", line 1065, in execute_sql
      cursor.execute(sql, params)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 100, in execute
      return super().execute(sql, params)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 68, in execute
      return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
      return executor(sql, params, many, context)
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 85, in _execute
      return self.cursor.execute(sql, params)
    File "/usr/local/lib/python3.6/dist-packages/django/db/utils.py", line 89, in __exit__
      raise dj_exc_value.with_traceback(traceback) from exc_value
    File "/usr/local/lib/python3.6/dist-packages/django/db/backends/utils.py", line 85, in _execute
      return self.cursor.execute(sql, params)
  django.db.utils.ProgrammingError: relation "objects_community" does not exist
  LINE 1: ...y"."state", "objects_community"."date_added" FROM "objects_c...

Alasdair · Accepted Answer

The traceback is telling you that your form ApartmentTableFormBuilder is causing a query Community.objects.all() when the module loads.

When you run migrate or makemigrations on a new database, this causes an error since the objects_community table hasn't been created yet.

The correct solution is to modify your form so that it doesn't cause any queries when the module loads. A hackier solution would be to temporarily comment out the code that is causing the issue until you have run makemigrations and migrate for the first time.

Django make migrations issue changing to new Postgres DB

Answers (1)

Related Questions