Fixed #8039 -- Make sure that extra(tables=...) tables are always included in

the resulting SQL. Previously, an optimisation was removing them in some corner
cases.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8429 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -542,7 +542,10 @@ class Query(object):
             first = False
         for t in self.extra_tables:
             alias, unused = self.table_alias(t)
-            if alias not in self.alias_map:
+            # Only add the alias if it's not already present (the table_alias()
+            # calls increments the refcount, so an alias refcount of one means
+            # this is the only reference.
+            if alias not in self.alias_map or self.alias_refcount[alias] == 1:
                 connector = not first and ', ' or ''
                 result.append('%s%s' % (connector, qn(alias)))
                 first = False

tests/regressiontests/extra_regress/models.py

@@ -24,6 +24,10 @@ class RevisionableModel(models.Model):
         new_revision.pk = None
         return new_revision
 
+class Order(models.Model):
+    created_by = models.ForeignKey(User)
+    text = models.TextField()
+
 __test__ = {"API_TESTS": """
 # Regression tests for #7314 and #7372
 
@@ -87,4 +91,11 @@ True
 >>> qs[:1]
 [<User: fred>]
 
+# Regression test for #8039: Ordering sometimes removed relevant tables from
+# extra(). This test is the critical case: ordering uses a table, but then
+# removes the reference because of an optimisation. The table should still be
+# present because of the extra() call.
+>>> Order.objects.extra(where=["username=%s"], params=["fred"], tables=["auth_user"]).order_by('created_by')
+[]
+
 """}