Replace dumb paginator with a time-limited one

src/auditlog/admin.py

@@ -1,17 +1,30 @@
+from django.conf import settings
 from django.contrib import admin
 from django.core.paginator import Paginator
+from django.db import connection, transaction, OperationalError
+from django.utils.functional import cached_property
 
 from .models import LogEntry
 from .mixins import LogEntryAdminMixin
 from .filters import ResourceTypeFilter
 
 
-class NoCountPaginator(Paginator):
-    PAGE_COUNT = 10000  # a large number
+class TimeLimitedPaginator(Paginator):
+    """A PostgreSQL-specific paginator with a hard time limit for total count of pages.
 
-    @property
+    Courtesy of https://medium.com/@hakibenita/optimizing-django-admin-paginator-53c4eb6bfca3
+    """
+    DEFAULT_PAGE_COUNT = 10000
+
+    @cached_property
     def count(self):
-        return self.per_page * self.PAGE_COUNT
+        timeout = getattr(settings, 'AUDITLOG_PAGINATOR_TIMEOUT', 500)  # ms
+        with transaction.atomic(), connection.cursor() as cursor:
+            cursor.execute('SET LOCAL statement_timeout TO %s;', (timeout,))
+            try:
+                return super().count
+            except OperationalError:
+                return self.per_page * self.DEFAULT_PAGE_COUNT
 
 
 class LogEntryAdmin(admin.ModelAdmin, LogEntryAdminMixin):
@@ -25,7 +38,7 @@ class LogEntryAdmin(admin.ModelAdmin, LogEntryAdminMixin):
     ]
     list_select_related = ['actor', 'content_type']
     show_full_result_count = False
-    paginator = NoCountPaginator
+    paginator = TimeLimitedPaginator
 
 
 admin.site.register(LogEntry, LogEntryAdmin)