Ticket #2256: queryset_count.3.patch

django/db/models/query.py

@@ -197 +197 @@
         "Performs a SELECT COUNT() and returns the number of records as an integer."
         counter = self._clone()
         counter._order_by = ()
+        counter._select_related = False
+        
+        offset = counter._offset
+        limit = counter._limit
         counter._offset = None
         counter._limit = None
-        counter._select_related = False
         
         try:
             select, sql, params = counter._get_sql_clause()
@@ -213 +216 @@
             cursor.execute("SELECT COUNT(DISTINCT(%s))" % id_col + sql, params)
         else:
             cursor.execute("SELECT COUNT(*)" + sql, params)
-        return cursor.fetchone()[0]
+        count = cursor.fetchone()[0]
 
+        # Apply any offset and limit since using LIMIT or OFFSET in SQL doesn't
+        # change the output of COUNT.
+        if offset:
+            count = max(0, count - offset)
+        if limit:
+            count = min(limit, count)
+
+        return count
+
     def get(self, *args, **kwargs):
         "Performs the SELECT and returns a single object matching the given keyword arguments."
         clone = self.filter(*args, **kwargs)

tests/modeltests/lookup/models.py

@@ -58 +58 @@
 >>> Article.objects.filter(headline__startswith='Blah blah').count()
 0L
 
+# count() should respect sliced query sets.
+>>> articles = Article.objects.all()
+>>> articles.count()
+7L
+>>> articles[:4].count()
+4
+>>> articles[1:100].count()
+6L
+>>> articles[10:100].count()
+0
+
 # Date and date/time lookups can also be done with strings.
 >>> Article.objects.filter(pub_date__exact='2005-07-27 00:00:00').count()
 3L