Merge pull request #1874 from pretix/perf2020

src/pretix/base/models/orders.py

@@ -902,7 +902,7 @@ class Order(LockModel, LoggedModel):
 
     @property
     def positions_with_tickets(self):
-        for op in self.positions.all():
+        for op in self.positions.select_related('item'):
             if not op.generate_ticket:
                 continue
             yield op
@@ -1155,7 +1155,7 @@ class AbstractPosition(models.Model):
         (2) questions: a list of Question objects, extended by an 'answer' property
         """
         self.answ = {}
-        for a in self.answers.all():
+        for a in getattr(self, 'answerlist', self.answers.all()):  # use prefetch_related cache from get_cart
             self.answ[a.question_id] = a
 
         # We need to clone our question objects, otherwise we will override the cached

src/pretix/base/services/quotas.py

@@ -113,10 +113,11 @@ class QuotaAvailability:
                 raise e
 
     def _write_cache(self, quotas, now_dt):
-        events = {q.event for q in quotas}
+        # We used to also delete item_quota_cache:* from the event cache here, but as the cache
+        # gets more complex, this does not seem worth it. The cache is only present for up to
+        # 5 seconds to prevent high peaks, and a 5-second delay in availability is usually
+        # tolerable
         update = []
-        for e in events:
-            e.cache.delete('item_quota_cache')
         for q in quotas:
             rewrite_cache = self._count_waitinglist and (
                 not q.cache_is_hot(now_dt) or self.results[q][0] > q.cached_availability_state