Fixed a problem when constructing complex select_related() calls.

Avoids joining with the wrong tables when connecting select_related() tables to
the main query. This also leads to slightly more efficient (meaning less tables
are joined) SQL queries in some other cases, too. Some unnecessary tables are
now trimmed that were not previously.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7741 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/queries/models.py

@@ -135,6 +135,24 @@ class ManagedModel(models.Model):
     def __unicode__(self):
         return self.data
 
+# An inter-related setup with multiple paths from Child to Detail.
+class Detail(models.Model):
+    data = models.CharField(max_length=10)
+
+class MemberManager(models.Manager):
+    def get_query_set(self):
+        return super(MemberManager, self).get_query_set().select_related("details")
+
+class Member(models.Model):
+    name = models.CharField(max_length=10)
+    details = models.OneToOneField(Detail, primary_key=True)
+
+    objects = MemberManager()
+
+class Child(models.Model):
+    person = models.OneToOneField(Member, primary_key=True)
+    parent = models.ForeignKey(Member, related_name="children")
+
 
 __test__ = {'API_TESTS':"""
 >>> t1 = Tag(name='t1')
@@ -720,5 +738,23 @@ appropriately.
 >>> Report.objects.values_list("creator__extra__info", flat=True).order_by("name")
 [u'e1', u'e2', None]
 
+Similarly for select_related(), joins beyond an initial nullable join must
+use outer joins so that all results are included.
+>>> Report.objects.select_related("creator", "creator__extra").order_by("name")
+[<Report: r1>, <Report: r2>, <Report: r3>]
+
+When there are multiple paths to a table from another table, we have to be
+careful not to accidentally reuse an inappropriate join when using
+select_related(). We used to return the parent's Detail record here by mistake.
+
+>>> d1 = Detail.objects.create(data="d1")
+>>> d2 = Detail.objects.create(data="d2")
+>>> m1 = Member.objects.create(name="m1", details=d1)
+>>> m2 = Member.objects.create(name="m2", details=d2)
+>>> c1 = Child.objects.create(person=m2, parent=m1)
+>>> obj = m1.children.select_related("person__details")[0]
+>>> obj.person.details.data
+u'd2'
+
 """}