Tolerate unknown fields coming from JOIN'd data

Author: Photonios

psqlextra/introspect/models.py

@@ -28,11 +28,11 @@ def _construct_model(
     apply_converters: bool = True
 ) -> TModel:
     fields_by_name_and_column = {}
-    for field in inspect_model_local_concrete_fields(model):
-        fields_by_name_and_column[field.attname] = field
+    for concrete_field in inspect_model_local_concrete_fields(model):
+        fields_by_name_and_column[concrete_field.attname] = concrete_field
 
-        if field.db_column:
-            fields_by_name_and_column[field.db_column] = field
+        if concrete_field.db_column:
+            fields_by_name_and_column[concrete_field.db_column] = concrete_field
 
     indexable_columns = list(columns)
 
@@ -41,9 +41,12 @@ def _construct_model(
     for index, value in enumerate(values):
         column = indexable_columns[index]
         try:
-            field = cast(Field, model._meta.get_field(column))
+            field: Optional[Field] = cast(Field, model._meta.get_field(column))
         except FieldDoesNotExist:
-            field = fields_by_name_and_column[column]
+            field = fields_by_name_and_column.get(column)
+
+        if not field:
+            continue
 
         field_column_expression = field.get_col(model._meta.db_table)
 

tests/test_introspect.py

@@ -415,3 +415,48 @@ def test_models_from_cursor_generator_efficiency(
 
         assert not next(instances_generator, None)
         assert cursor.rownumber == 2
+
+
+@pytest.mark.skipif(
+    django.VERSION < (3, 1),
+    reason=django_31_skip_reason,
+)
+def test_models_from_cursor_tolerates_additional_columns(
+    mocked_model_foreign_keys, mocked_model_varying_fields
+):
+    with connection.cursor() as cursor:
+        cursor.execute(
+            f"ALTER TABLE {mocked_model_foreign_keys._meta.db_table} ADD COLUMN new_col text DEFAULT NULL"
+        )
+        cursor.execute(
+            f"ALTER TABLE {mocked_model_varying_fields._meta.db_table} ADD COLUMN new_col text DEFAULT NULL"
+        )
+
+    instance = mocked_model_foreign_keys.objects.create(
+        varying_fields=mocked_model_varying_fields.objects.create(
+            title="test", updated_at=timezone.now()
+        ),
+        single_field=None,
+    )
+
+    with connection.cursor() as cursor:
+        cursor.execute(
+            f"""
+            SELECT fk_t.*, vf_t.* FROM {mocked_model_foreign_keys._meta.db_table} fk_t
+            INNER JOIN {mocked_model_varying_fields._meta.db_table} vf_t ON vf_t.id = fk_t.varying_fields_id
+        """
+        )
+
+        queried_instances = list(
+            models_from_cursor(
+                mocked_model_foreign_keys,
+                cursor,
+                related_fields=["varying_fields"],
+            )
+        )
+
+        assert len(queried_instances) == 1
+        assert queried_instances[0].id == instance.id
+        assert (
+            queried_instances[0].varying_fields.id == instance.varying_fields.id
+        )