Fixed bug in which DISTINCT clauses were forcibly removed from supplied querysets

Makefile

@@ -9,7 +9,7 @@ help:  ## show help
 install: ## install all requirements including for testing
 	pip install -r requirements-dev.txt
 
-install-quite:  ## same as install but pipes all output to /dev/null
+install-quiet:  ## same as install but pipes all output to /dev/null
 	pip install -r requirements-dev.txt > /dev/null
 
 clean: clean-build clean-pyc  ## remove all artifacts

url_filter/backends/django.py

@@ -113,7 +113,8 @@ def filter_by_specs(self, queryset):
             queryset = queryset.exclude(**{lookup: value})
 
         to_many = self._is_any_to_many()
-        return queryset.distinct() if to_many and (include or exclude) else queryset
+        is_distinct = queryset.distinct()
+        return queryset.distinct() if (not is_distinct) and to_many and (include or exclude) else queryset
 
     def _is_any_to_many(self):
         return any(self._is_to_many(self.model, i.components) for i in self.regular_specs)