Tengo un proyecto Django heredado (django-1.1.29) y algunas pruebas en pytest (pytest-4.3.0), todas ejecutándose dentro de Docker. La base de datos es PostgreSQL 10 y es un servicio docker-compose del que depende la aplicación. La versión de Python es 2.7.18.

Últimamente las pruebas empezaron a fallar con un extraño error:

InternalError: variable not found in subplan target list .

El error ocurre solo cuando cuento la cantidad de objetos de un determinado modelo, por ejemplo, Problem.objects.count() . La instrucción se convierte en la siguiente consulta

(0.000) SELECT COUNT(*) AS "__count" FROM "problems_problem"; args=() por Django.

El registro completo está aquí:

 self = <integration_tests.project_name.subjects.test_views.test_theme_problem_view_set.TestThemeProblemViewSet object at 0x7f01faccbe50> jclient = <project_name.common.test_utils.json_client.JSONClient object at 0x7f01fadb8ed0> def test_all_is_ok(self, jclient, subject_model, content_manager): url, data = self._main_prepare(jclient, subject_model, content_manager) response = jclient.post_json(url, data[0]) assert response.status_code == 201 > assert Problem.objects.count() == 1 integration_tests/project_name/subjects/test_views/test_theme_problem_view_set.py:86: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ /usr/local/lib/python2.7/dist-packages/django/db/models/manager.py:85: in manager_method return getattr(self.get_queryset(), name)(*args, **kwargs) /usr/local/lib/python2.7/dist-packages/django/db/models/query.py:364: in count return self.query.get_count(using=self.db) /usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py:499: in get_count number = obj.get_aggregation(using, ['__count'])['__count'] /usr/local/lib/python2.7/dist-packages/django/db/models/sql/query.py:480: in get_aggregation result = compiler.execute_sql(SINGLE) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ self = <django.db.models.sql.compiler.SQLCompiler object at 0x7f01faee3a50> result_type = 'single', chunked_fetch = False def execute_sql(self, result_type=MULTI, chunked_fetch=False): """ Run the query against the database and returns the result(s). The return value is a single data item if result_type is SINGLE, or an iterator over the results if the result_type is MULTI. result_type is either MULTI (use fetchmany() to retrieve all rows), SINGLE (only retrieve a single row), or None. In this last case, the cursor is returned if any query is executed, since it's used by subclasses such as InsertQuery). It's possible, however, that no query is needed, as the filters describe an empty set. In that case, None is returned, to avoid any unnecessary database interaction. """ if not result_type: result_type = NO_RESULTS try: sql, params = self.as_sql() if not sql: raise EmptyResultSet except EmptyResultSet: if result_type == MULTI: return iter([]) else: return if chunked_fetch: cursor = self.connection.chunked_cursor() else: cursor = self.connection.cursor() try: cursor.execute(sql, params) except Exception as original_exception: try: # Might fail for server-side cursors (eg connection closed) cursor.close() except Exception: # Ignore clean up errors and raise the original error instead. # Python 2 doesn't chain exceptions. Remove this error # silencing when dropping Python 2 compatibility. pass > raise original_exception E InternalError: variable not found in subplan target list /usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py:899: InternalError

Realmente agradecería si alguien pudiera ayudarme a solucionar este problema o al menos dar algunos consejos sobre dónde encontrar las razones.

Esto es lo que he intentado hacer hasta ahora, pero ninguno de estos ayudó:

• Use diferentes versiones de PostgreSQL (10, 11, 12, 13)
• Deshabilitar el cursor del lado del servidor