Optimize competences queries

server/vbv_lernwelt/dashboard/graphql/types/competence.py

@@ -1,10 +1,13 @@
 from typing import List, Tuple
 
 import graphene
+import structlog
 from wagtail.models import Page
 
 from vbv_lernwelt.course.models import CourseCompletion, CourseCompletionStatus
 
+logger = structlog.get_logger(__name__)
+
 
 class CompetencePerformanceStatisticsSummaryType(graphene.ObjectType):
     _id = graphene.ID(required=True)
@@ -41,25 +44,23 @@ def competences(
     completions = CourseCompletion.objects.filter(
         course_session_id__in=course_session_selection_ids,
         page_type="competence.PerformanceCriteria",
-    ).prefetch_related("course_session", "page")
+    ).select_related("course_session", "page")
 
     if user_selection_ids is not None:
         completions = completions.filter(user_id__in=user_selection_ids)
 
-    competence_records = {}
+    page_ids = completions.values_list("page_id", flat=True).distinct()
+    pages = Page.objects.filter(id__in=page_ids)
+    learning_units = {page.id: page.specific.learning_unit for page in pages}
 
-    unique_page_ids = {completion.page.id for completion in completions}
-    learning_units = {
-        page_id: Page.objects.get(id=page_id).specific.learning_unit
-        for page_id in unique_page_ids
-    }
     circles = {
         lu.id: c
         for lu in learning_units.values()
-        if (lu is not None and (c := lu.get_circle()) is not None)
-        and (circle_ids is None or c.id in circle_ids)
+        if lu and (c := lu.get_circle()) and (circle_ids is None or c.id in circle_ids)
     }
 
+    competence_records = {}
+
     for completion in completions:
         learning_unit = learning_units.get(completion.page.id)
 
@@ -73,20 +74,23 @@ def competences(
 
         combined_id = f"{circle.id}-{completion.course_session.id}@{urql_id_postfix}"
 
-        competence_records.setdefault(combined_id, {}).setdefault(
-            learning_unit,
-            CompetenceRecordStatisticsType(
-                _id=combined_id,  # noqa
-                title=learning_unit.title,  # noqa
-                course_session_id=completion.course_session.id,  # noqa
-                generation=completion.course_session.generation,  # noqa
-                circle_id=circle.id,  # noqa
-                success_count=0,  # noqa
-                fail_count=0,  # noqa
+        if combined_id not in competence_records:
+            competence_records[combined_id] = {}
+
+        if learning_unit not in competence_records[combined_id]:
+            competence_records[combined_id][
+                learning_unit
+            ] = CompetenceRecordStatisticsType(
+                _id=combined_id,
+                title=learning_unit.title,
+                course_session_id=completion.course_session.id,
+                generation=completion.course_session.generation,
+                circle_id=circle.id,
+                success_count=0,
+                fail_count=0,
                 details_url=f"/course/{course_slug}/cockpit?courseSessionId={completion.course_session.id}",
                 # noqa
-            ),
-        )
+            )
 
         if completion.completion_status == CourseCompletionStatus.SUCCESS.value:
             competence_records[combined_id][learning_unit].success_count += 1
@@ -99,7 +103,7 @@ def competences(
         for record in circle_records.values()
     ]
 
-    success_count = sum([c.success_count for c in values])
-    fail_count = sum([c.fail_count for c in values])
+    success_count = sum(c.success_count for c in values)
+    fail_count = sum(c.fail_count for c in values)
 
     return values, success_count, fail_count