Vfrdtyky

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 <module>

      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 "<frozen importlib._bootstrap>", line 994, in _gcd_import

    File "<frozen importlib._bootstrap>", line 971, in _find_and_load

    File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked

    File "<frozen importlib._bootstrap>", line 665, in _load_unlocked

    File "<frozen importlib._bootstrap_external>", line 678, in exec_module

    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed

    File "/home/viatech/Projects/ExactEstate/ExactEstate/ExactEstate/urls.py", line 21, in <module>

      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 "<frozen importlib._bootstrap>", line 994, in _gcd_import

    File "<frozen importlib._bootstrap>", line 971, in _find_and_load

    File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked

    File "<frozen importlib._bootstrap>", line 665, in _load_unlocked

    File "<frozen importlib._bootstrap_external>", line 678, in exec_module

    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed

    File "/home/viatech/Projects/ExactEstate/ExactEstate/interface_admin/urls.py", line 2, in <module>

      from interface_admin import views

    File "/home/viatech/Projects/ExactEstate/ExactEstate/interface_admin/views.py", line 4, in <module>

      from forms import RegistrationForm, SQLForm, SingleFileUploadForm, ApartmentTableFormBuilder

    File "/home/viatech/Projects/ExactEstate/ExactEstate/forms/ApartmentTableFormBuilder.py", line 10, in <module>

      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...

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.