[Backport] Improving performance for history api

taiga/projects/history/api.py

@@ -102,8 +102,8 @@ class HistoryViewSet(ReadOnlyListViewSet):
     def retrieve(self, request, pk):
         obj = self.get_object()
         self.check_permissions(request, "retrieve", obj)
-
         qs = services.get_history_queryset_by_model_instance(obj)
+        qs = services.prefetch_owners_in_history_queryset(qs)
         return self.response_for_queryset(qs)
 
 

taiga/projects/history/models.py

@@ -78,6 +78,8 @@ class HistoryEntry(models.Model):
     is_snapshot = models.BooleanField(default=False)
 
     _importing = None
+    _owner = None
+    _prefetched_owner = False
 
     @cached_property
     def is_change(self):
@@ -91,14 +93,23 @@ class HistoryEntry(models.Model):
     def is_delete(self):
       return self.type == HistoryType.delete
 
-    @cached_property
+    @property
     def owner(self):
-        pk = self.user["pk"]
-        model = get_user_model()
-        try:
-            return model.objects.get(pk=pk)
-        except model.DoesNotExist:
-            return None
+        if not self._prefetched_owner:
+            pk = self.user["pk"]
+            model = get_user_model()
+            try:
+                owner = model.objects.get(pk=pk)
+            except model.DoesNotExist:
+                owner = None
+
+            self.prefetch_owner(owner)
+
+        return self._owner
+
+    def prefetch_owner(self, owner):
+        self._owner = owner
+        self._prefetched_owner = True
 
     @cached_property
     def values_diff(self):

taiga/projects/history/services.py

@@ -33,6 +33,7 @@ from functools import wraps
 from functools import lru_cache
 
 from django.conf import settings
+from django.contrib.auth import get_user_model
 from django.contrib.contenttypes.models import ContentType
 from django.core.paginator import Paginator, InvalidPage
 from django.apps import apps
@@ -352,6 +353,16 @@ def get_history_queryset_by_model_instance(obj:object, types=(HistoryType.change
     return qs.order_by("created_at")
 
 
+def prefetch_owners_in_history_queryset(qs):
+    user_ids = [u["pk"] for u in qs.values_list("user", flat=True)]
+    users = get_user_model().objects.filter(id__in=user_ids)
+    users_by_id = {u.id: u for u in users}
+    for history_entry in  qs:
+        history_entry.prefetch_owner(users_by_id.get(history_entry.user["pk"], None))
+
+    return qs
+
+
 # Freeze implementatitions
 from .freeze_impl import project_freezer
 from .freeze_impl import milestone_freezer