fix: Fix evironment metadata N+1 for environments list

api/environments/tests/test_views.py

@@ -1,8 +1,10 @@
 import json
+from typing import Callable
 from unittest import TestCase, mock
 
 import pytest
 from core.constants import STRING
+from django.contrib.contenttypes.models import ContentType
 from django.urls import reverse
 from pytest_lazyfixture import lazy_fixture
 from rest_framework import status
@@ -12,9 +14,10 @@
 from environments.identities.models import Identity
 from environments.identities.traits.models import Trait
 from environments.models import Environment, EnvironmentAPIKey, Webhook
+from environments.permissions.constants import VIEW_ENVIRONMENT
 from environments.permissions.models import UserEnvironmentPermission
 from features.models import Feature, FeatureState
-from metadata.models import Metadata
+from metadata.models import Metadata, MetadataModelField
 from organisations.models import Organisation, OrganisationRole
 from projects.models import (
     Project,
@@ -536,6 +539,53 @@ def test_create_environment_without_required_metadata_returns_400(
     assert "Missing required metadata field" in response.json()["metadata"][0]
 
 
+def test_view_environment_with_staff_track_query_count(
+    staff_client: FFAdminUser,
+    environment: Environment,
+    with_environment_permissions: Callable,
+    project: Project,
+    django_assert_num_queries: Callable,
+    environment_metadata_a: Metadata,
+    environment_metadata_b: Metadata,
+    required_a_environment_metadata_field: MetadataModelField,
+    environment_content_type: ContentType,
+) -> None:
+    # Given
+    with_environment_permissions([VIEW_ENVIRONMENT])
+
+    url = reverse("api-v1:environments:environment-list")
+    data = {"project": project.id}
+
+    # When
+    expected_query_count = 7
+    with django_assert_num_queries(expected_query_count):
+        response = staff_client.get(url, data=data, content_type="application/json")
+
+    assert response.status_code == status.HTTP_200_OK
+
+    # Add an environment to make sure the query count is the same.
+    environment_2 = Environment.objects.create(
+        name="Second Environment", project=project
+    )
+    Metadata.objects.create(
+        object_id=environment_2.id,
+        content_type=environment_content_type,
+        model_field=required_a_environment_metadata_field,
+        field_value="10",
+    )
+
+    with_environment_permissions([VIEW_ENVIRONMENT], environment_id=environment_2.id)
+
+    # One additional query for an unrelated, unfixable N+1 issue.
+    expected_query_count += 1
+
+    # Then
+    with django_assert_num_queries(expected_query_count):
+        response = staff_client.get(url, data=data, content_type="application/json")
+
+    assert response.status_code == status.HTTP_200_OK
+
+
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],

api/environments/views.py

@@ -98,7 +98,7 @@ def get_queryset(self):
                 raise ValidationError("Invalid or missing value for project parameter.")
 
             return self.request.user.get_permitted_environments(
-                "VIEW_ENVIRONMENT", project=project
+                "VIEW_ENVIRONMENT", project=project, prefetch_metadata=True
             )
 
         # Permission class handles validation of permissions for other actions

api/permissions/permission_service.py

@@ -104,6 +104,7 @@ def get_permitted_environments_for_user(
     project: Project,
     permission_key: str,
     tag_ids: List[int] = None,
+    prefetch_metadata: bool = False,
 ) -> QuerySet[Environment]:
     """
     Get all environments that the user has the given permissions for.
@@ -130,7 +131,16 @@ def get_permitted_environments_for_user(
     )
     filter_ = base_filter & Q(project=project)
 
-    return Environment.objects.filter(filter_).distinct().defer("description")
+    queryset = Environment.objects.filter(filter_)
+    if prefetch_metadata:
+        queryset = queryset.prefetch_related("metadata")
+
+    # Description is defered due to Oracle support where a
+    # query can't have a where clause if description is in
+    # the select parameters. This leads to an N+1 query for
+    # lists of environments when description is included, as
+    # each environment object re-queries the DB seperately.
+    return queryset.distinct().defer("description")
 
 
 def get_permitted_environments_for_master_api_key(

api/users/models.py

@@ -272,10 +272,14 @@ def is_project_admin(self, project: Project) -> bool:
         return is_user_project_admin(self, project)
 
     def get_permitted_environments(
-        self, permission_key: str, project: Project, tag_ids: typing.List[int] = None
+        self,
+        permission_key: str,
+        project: Project,
+        tag_ids: typing.List[int] = None,
+        prefetch_metadata: bool = False,
     ) -> QuerySet[Environment]:
         return get_permitted_environments_for_user(
-            self, project, permission_key, tag_ids
+            self, project, permission_key, tag_ids, prefetch_metadata=prefetch_metadata
         )
 
     @staticmethod