fix _get_distinct_timezone

the previous query did not actually get distinct timezones

Author: beedub

django_celery_beat/schedulers.py

@@ -1,4 +1,6 @@
 """Beat Scheduler Implementation."""
+from __future__ import annotations
+
 import datetime
 import logging
 import math
@@ -340,7 +342,7 @@ def _get_crontab_exclude_query(self):
                             + 24
                         ) % 24
                     )
-                    for timezone_name in self._get_unique_timezone_names()
+                    for timezone_name in self._get_unique_timezones()
                 ],
                 # Default case - use hour as is
                 default=F('hour_int')
@@ -359,11 +361,17 @@ def _get_crontab_exclude_query(self):
 
         return exclude_query
 
-    def _get_unique_timezone_names(self):
-        """Get a list of all unique timezone names used in CrontabSchedule"""
-        return CrontabSchedule.objects.values_list(
-            'timezone', flat=True
-        ).distinct()
+    def _get_unique_timezones(self) -> list[ZoneInfo]:
+        """Get a list of all unique timezones used in CrontabSchedule"""
+        return list(
+            CrontabSchedule.objects.order_by(
+                'timezone'
+            ).distinct(
+                'timezone'
+            ).values_list(
+                'timezone', flat=True
+            )
+        )
 
     def _get_timezone_offset(self, timezone_name):
         """

t/unit/test_schedulers.py

@@ -1059,6 +1059,21 @@ def test_crontab_special_hour_four(self):
         # The hour=4 task should never be excluded
         assert task_hour_four.id not in excluded_tasks
 
+    @pytest.mark.django_db
+    def test_get_unique_timezones(self):
+        """
+        Test that get unique timezones returns a list of unique timezones
+        """
+        # Create 2 crontabs with same timezone, and 1 with different timezone
+        CrontabSchedule.objects.create(hour='4', timezone='UTC')
+        CrontabSchedule.objects.create(hour='4', timezone='UTC')
+        CrontabSchedule.objects.create(hour='4', timezone='America/New_York')
+
+        timezones = self.s._get_unique_timezones()
+
+        assert len(timezones) == 2
+        assert set(timezones) == {ZoneInfo('UTC'), ZoneInfo('America/New_York')}
+
     @pytest.mark.django_db
     @patch('django_celery_beat.schedulers.aware_now')
     @patch('django.utils.timezone.get_current_timezone')