[1.2.X] Fixed #12687 -- fixed an issue with aggregates and counts in conjunction with annotations where the QuerySet was provably empty. Backport of [14586].

alex · alex · commit 03b111c6cc2a · 2010-11-17T02:58:59.000Z
git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14587 bcc190cf-cafb-0310-a4f2-bffc1f526a37
diff --git a/django/db/models/sql/aggregates.py b/django/db/models/sql/aggregates.py
@@ -8,6 +8,7 @@ class AggregateField(object):
     """
     def __init__(self, internal_type):
         self.internal_type = internal_type
+
     def get_internal_type(self):
         return self.internal_type
 
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
@@ -337,7 +337,7 @@ def get_aggregation(self, using):
         # information but retrieves only the first row. Aggregate
         # over the subquery instead.
         if self.group_by is not None:
-            from subqueries import AggregateQuery
+            from django.db.models.sql.subqueries import AggregateQuery
             query = AggregateQuery(self.model)
 
             obj = self.clone()
@@ -349,7 +349,13 @@ def get_aggregation(self, using):
                     query.aggregate_select[alias] = aggregate
                     del obj.aggregate_select[alias]
 
-            query.add_subquery(obj, using)
+            try:
+                query.add_subquery(obj, using)
+            except EmptyResultSet:
+                return dict(
+                    (alias, None)
+                    for alias in query.aggregate_select
+                )
         else:
             query = self
             self.select = []
@@ -382,13 +388,19 @@ def get_count(self, using):
             # If a select clause exists, then the query has already started to
             # specify the columns that are to be returned.
             # In this case, we need to use a subquery to evaluate the count.
-            from subqueries import AggregateQuery
+            from django.db.models.sql.subqueries import AggregateQuery
             subquery = obj
             subquery.clear_ordering(True)
             subquery.clear_limits()
 
             obj = AggregateQuery(obj.model)
-            obj.add_subquery(subquery, using=using)
+            try:
+                obj.add_subquery(subquery, using=using)
+            except EmptyResultSet:
+                # add_subquery evaluates the query, if it's an EmptyResultSet
+                # then there are can be no results, and therefore there the
+                # count is obviously 0
+                return 0
 
         obj.add_count_column()
         number = obj.get_aggregation(using=using)[None]
diff --git a/django/db/models/sql/subqueries.py b/django/db/models/sql/subqueries.py
@@ -10,6 +10,7 @@
 from django.db.models.sql.query import Query
 from django.db.models.sql.where import AND, Constraint
 
+
 __all__ = ['DeleteQuery', 'UpdateQuery', 'InsertQuery', 'DateQuery',
         'AggregateQuery']
 
diff --git a/tests/regressiontests/aggregation_regress/tests.py b/tests/regressiontests/aggregation_regress/tests.py
@@ -641,6 +641,24 @@ def test_more_more_more(self):
             lambda: Book.objects.annotate(mean_age=Avg('authors__age')).annotate(Avg('mean_age'))
         )
 
+    def test_empty_filter_count(self):
+        self.assertEqual(
+            Author.objects.filter(id__in=[]).annotate(Count("friends")).count(),
+            0
+        )
+
+    def test_empty_filter_aggregate(self):
+        self.assertEqual(
+            Author.objects.filter(id__in=[]).annotate(Count("friends")).aggregate(Count("pk")),
+            {"pk__count": None}
+        )
+
+    def test_annotate_and_join(self):
+        self.assertEqual(
+            Author.objects.annotate(c=Count("friends__name")).exclude(friends__name="Joe").count(),
+            Author.objects.count()
+        )
+
     if run_stddev_tests():
         def test_stddev(self):
             self.assertEqual(
