fix: optimize queries for DocumentChangesFeed (#5675)

ietf/doc/feeds.py

@@ -45,7 +45,7 @@ def subtitle(self, obj):
         return "History of change entries for %s." % obj.display_name()
 
     def items(self, obj):
-        events = obj.docevent_set.all().order_by("-time","-id")
+        events = obj.docevent_set.all().order_by("-time","-id").select_related("by", "newrevisiondocevent", "submissiondocevent")
         augment_events_with_revision(obj, events)
         return events
 

ietf/doc/utils.py

@@ -17,6 +17,7 @@
 
 from django.conf import settings
 from django.contrib import messages
+from django.db.models import QuerySet
 from django.forms import ValidationError
 from django.http import Http404
 from django.template.loader import render_to_string
@@ -344,11 +345,18 @@ def augment_events_with_revision(doc, events):
     """Take a set of events for doc and add a .rev attribute with the
     revision they refer to by checking NewRevisionDocEvents."""
 
-    event_revisions = list(NewRevisionDocEvent.objects.filter(doc=doc).order_by('time', 'id').values('id', 'rev', 'time'))
+    if isinstance(events, QuerySet):
+        qs = events.filter(newrevisiondocevent__isnull=False)
+    else:
+        qs = NewRevisionDocEvent.objects.filter(doc=doc)
+    event_revisions = list(qs.order_by('time', 'id').values('id', 'rev', 'time'))
 
     if doc.type_id == "draft" and doc.get_state_slug() == "rfc":
         # add fake "RFC" revision
-        e = doc.latest_event(type="published_rfc")
+        if isinstance(events, QuerySet):
+            e = events.filter(type="published_rfc").order_by('time').last()
+        else:
+            e = doc.latest_event(type="published_rfc")
         if e:
             event_revisions.append(dict(id=e.id, time=e.time, rev="RFC"))
             event_revisions.sort(key=lambda x: (x["time"], x["id"]))