Cast object id lookup to pk field type

watson/search.py

@@ -15,6 +15,7 @@ from django.core.exceptions import ImproperlyConfigured, ObjectDoesNotExist
 from django.db import models, connections, router
 from django.db.models import Q
 from django.db.models.expressions import RawSQL
+from django.db.models.functions import Coalesce
 from django.db.models.query import QuerySet
 from django.db.models.signals import post_save, pre_delete
 from django.utils.encoding import force_str
@@ -445,21 +446,21 @@ class SearchEngine(object):
     def _get_deleted_entries_for_model(self, model):
         """Returns a queryset of entries associated with deleted object instances of the given model"""
         from django.contrib.contenttypes.models import ContentType
-        from watson.models import SearchEntry, has_int_pk
+        from watson.models import SearchEntry
         content_type = ContentType.objects.get_for_model(model)
-        # subquery to get entries which cannot be found in the original table (when negated)
-        lookup_subquery = models.Subquery(
-            model.objects.all().values('pk')
-        )
-        # map the lookup to the appropriate id field
-        if has_int_pk(model):
-            id_lookup = {'object_id_int__in': lookup_subquery}
-        else:
-            id_lookup = {'object_id__in': lookup_subquery}
-        return SearchEntry.objects.filter(
+        id_output_field = type(model._meta.pk)
+        return SearchEntry.objects.annotate(
+            # normalize the object id into a single field of the correct type
+            normalized_pk=Coalesce('object_id_int', 'object_id', output_field=id_output_field())
+        ).filter(
             Q(content_type=content_type) &
             Q(engine_slug=self._engine_slug) &
-            ~Q(**id_lookup)
+            # subquery to get entries which cannot be found in the original table (when negated)
+            ~Q(
+                normalized_pk__in=models.Subquery(
+                    model.objects.all().values('pk')
+                )
+            )
         )
 
     def _get_entries_for_obj(self, obj):