Add support for relational lookups on ObjectsByDateTracker

trackstats/trackers.py

@@ -5,6 +5,7 @@
 from django.db import models
 from django.db import connections
 from django.utils import timezone
+from functools import reduce
 
 from .models import Period, StatisticByDate, StatisticByDateAndObject
 
@@ -20,6 +21,9 @@ def __init__(self, **kwargs):
         for prop, val in kwargs.items():
             setattr(self, prop, val)
 
+    def _get_start_date(self, obj, start_date):
+        return
+
     def get_most_recent_kwargs(self):
         most_recent_kwargs = {
             'metric': self.metric,
@@ -37,7 +41,7 @@ def get_start_date(self, qs):
             if first_instance is None:
                 # No data
                 return
-            start_date = getattr(first_instance, self.date_field)
+            start_date = reduce(getattr, self.date_field.split('__'), first_instance)
         if start_date and isinstance(start_date, datetime):
             if timezone.is_aware(start_date):
                 start_date = timezone.make_naive(start_date).date()