Improve performance of global order search

src/pretix/control/views/__init__.py

@@ -1,3 +1,10 @@
+import collections
+import warnings
+
+from django.core.paginator import (
+    EmptyPage, PageNotAnInteger, UnorderedObjectListWarning,
+)
+from django.utils.translation import ugettext_lazy as _
 from django.views.generic import edit
 
 
@@ -56,3 +63,122 @@ class PaginationMixin:
         ctx = super().get_context_data(**kwargs)
         ctx['page_size'] = self.get_paginate_by(None)
         return ctx
+
+
+class LargeResultSetPage(collections.Sequence):
+
+    def __init__(self, object_list, number, paginator):
+        self.object_list = object_list
+        self.number = number
+        self.paginator = paginator
+
+    def __repr__(self):
+        return '<Page %s>' % self.number
+
+    def __len__(self):
+        return len(self.object_list)
+
+    def __getitem__(self, index):
+        if not isinstance(index, (slice, int)):
+            raise TypeError
+        # The object_list is converted to a list so that if it was a QuerySet
+        # it won't be a database hit per __getitem__.
+        if not isinstance(self.object_list, list):
+            self.object_list = list(self.object_list)
+        return self.object_list[index]
+
+    def has_next(self):
+        try:
+            return self[self.paginator.per_page - 1]
+        except:
+            return False
+
+    def has_previous(self):
+        return self.number > 1
+
+    def has_other_pages(self):
+        return self.has_previous() or self.has_next()
+
+    def next_page_number(self):
+        return self.paginator.validate_number(self.number + 1)
+
+    def previous_page_number(self):
+        return self.paginator.validate_number(self.number - 1)
+
+    def start_index(self):
+        """
+        Returns the 1-based index of the first object on this page,
+        relative to total objects in the paginator.
+        """
+        # Special case, return zero if no items.
+        if self.paginator.count == 0:
+            return 0
+        return (self.paginator.per_page * (self.number - 1)) + 1
+
+    def end_index(self):
+        """
+        Returns the 1-based index of the last object on this page,
+        relative to total objects found (hits).
+        """
+        # Special case for the last page because there can be orphans.
+        if self.number == self.paginator.num_pages:
+            return self.paginator.count
+        return self.number * self.paginator.per_page
+
+
+class LargeResultSetPaginator(object):
+
+    def __init__(self, object_list, per_page, orphans=0,
+                 allow_empty_first_page=True):
+        self.object_list = object_list
+        self._check_object_list_is_ordered()
+        self.per_page = int(per_page)
+        self.orphans = int(orphans)
+
+    def validate_number(self, number):
+        """
+        Validates the given 1-based page number.
+        """
+        try:
+            number = int(number)
+        except (TypeError, ValueError):
+            raise PageNotAnInteger(_('That page number is not an integer'))
+        if number < 1:
+            raise EmptyPage(_('That page number is less than 1'))
+        return number
+
+    def page(self, number):
+        """
+        Returns a Page object for the given 1-based page number.
+        """
+        number = self.validate_number(number)
+        bottom = (number - 1) * self.per_page
+        top = bottom + self.per_page
+        return self._get_page(self.object_list[bottom:top], number, self)
+
+    def _get_page(self, *args, **kwargs):
+        """
+        Returns an instance of a single page.
+
+        This hook can be used by subclasses to use an alternative to the
+        standard :cls:`Page` object.
+        """
+        return LargeResultSetPage(*args, **kwargs)
+
+    def _check_object_list_is_ordered(self):
+        """
+        Warn if self.object_list is unordered (typically a QuerySet).
+        """
+        ordered = getattr(self.object_list, 'ordered', None)
+        if ordered is not None and not ordered:
+            obj_list_repr = (
+                '{} {}'.format(self.object_list.model, self.object_list.__class__.__name__)
+                if hasattr(self.object_list, 'model')
+                else '{!r}'.format(self.object_list)
+            )
+            warnings.warn(
+                'Pagination may yield inconsistent results with an unordered '
+                'object_list: {}.'.format(obj_list_repr),
+                UnorderedObjectListWarning,
+                stacklevel=3
+            )

src/pretix/control/views/search.py

@@ -1,14 +1,15 @@
-from django.db.models import Count, Q
+from django.db.models import Q
 from django.utils.functional import cached_property
 from django.views.generic import ListView
 
 from pretix.base.models import Order
 from pretix.control.forms.filter import OrderSearchFilterForm
-from pretix.control.views import PaginationMixin
+from pretix.control.views import LargeResultSetPaginator, PaginationMixin
 
 
 class OrderSearch(PaginationMixin, ListView):
     model = Order
+    paginator_class = LargeResultSetPaginator
     context_object_name = 'orders'
     template_name = 'pretixcontrol/search/orders.html'
 
@@ -22,7 +23,7 @@ class OrderSearch(PaginationMixin, ListView):
         return ctx
 
     def get_queryset(self):
-        qs = Order.objects.all().annotate(pcnt=Count('positions', distinct=True)).select_related('invoice_address')
+        qs = Order.objects.select_related('invoice_address')
         if not self.request.user.is_superuser:
             qs = qs.filter(
                 Q(event__organizer_id__in=self.request.user.teams.filter(
@@ -34,7 +35,7 @@ class OrderSearch(PaginationMixin, ListView):
         if self.filter_form.is_valid():
             qs = self.filter_form.filter_qs(qs)
 
-        return qs.distinct().only(
+        return qs.only(
             'id', 'invoice_address__name', 'code', 'event', 'email', 'datetime', 'total', 'status'
         ).prefetch_related(
             'event', 'event__organizer'