Fixed a problem with values() and values_list() queries and nullable joins.

Previously, if we were querying across a nullable join and then a non-nullable
one, the second join would not be a LEFT OUTER join, which would exclude
certain valid results from the result set.

This is the same problem as [7597] but for values() field specifications, so
this covers the second case where Django adds extra stuff to the select-clause.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7740 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -679,12 +679,16 @@ class Query(object):
         for the join to contain NULL values on the left. If 'unconditional' is
         False, the join is only promoted if it is nullable, otherwise it is
         always promoted.
+
+        Returns True if the join was promoted.
         """
         if ((unconditional or self.alias_map[alias][NULLABLE]) and
                 self.alias_map[alias] != self.LOUTER):
             data = list(self.alias_map[alias])
             data[JOIN_TYPE] = self.LOUTER
             self.alias_map[alias] = tuple(data)
+            return True
+        return False
 
     def change_aliases(self, change_map):
         """
@@ -1294,10 +1298,12 @@ class Query(object):
                         final_alias = join[LHS_ALIAS]
                         col = join[LHS_JOIN_COL]
                         joins = joins[:-1]
+                promote = False
                 for join in joins[1:]:
                     # Only nullable aliases are promoted, so we don't end up
                     # doing unnecessary left outer joins here.
-                    self.promote_alias(join)
+                    if self.promote_alias(join, promote):
+                        promote = True
                 self.select.append((final_alias, col))
                 self.select_fields.append(field)
         except MultiJoin:

tests/regressiontests/queries/models.py

@@ -58,7 +58,7 @@ class Item(models.Model):
 
 class Report(models.Model):
     name = models.CharField(max_length=10)
-    creator = models.ForeignKey(Author, to_field='num')
+    creator = models.ForeignKey(Author, to_field='num', null=True)
 
     def __unicode__(self):
         return self.name
@@ -191,6 +191,8 @@ by 'info'. Helps detect some problems later.
 >>> r1.save()
 >>> r2 = Report(name='r2', creator=a3)
 >>> r2.save()
+>>> r3 = Report(name='r3')
+>>> r3.save()
 
 Ordering by 'rank' gives us rank2, rank1, rank3. Ordering by the Meta.ordering
 will be rank3, rank2, rank1.
@@ -713,5 +715,10 @@ in MySQL. This exercises that case.
 >>> mm = ManagedModel.objects.create(data='mm1', tag=t1, is_public=True)
 >>> ManagedModel.objects.update(data='mm')
 
+A values() or values_list() query across joined models must use outer joins
+appropriately.
+>>> Report.objects.values_list("creator__extra__info", flat=True).order_by("name")
+[u'e1', u'e2', None]
+
 """}