[1.7.x] Fixed #23605 -- Fixed nested subquery regression

Added relabeled_clone() method to sql.Query to fix the problem. It
manifested itself in rare cases where at least double nested subquery's
filter condition might target non-existing alias.

Thanks to Trac alias ris for reporting the problem.

Backport of 5c481db29572a387651681b43d5d4523f96b3793 from master

5 files changed, 77 insertions, 3 deletions

diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index d8697fa06d..90ac90f9ae 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -56,7 +56,7 @@ class SQLCompiler(object):
         if name in self.quote_cache:
             return self.quote_cache[name]
         if ((name in self.query.alias_map and name not in self.query.table_map) or
-                name in self.query.extra_select):
+                name in self.query.extra_select or name in self.query.external_aliases):
             self.quote_cache[name] = name
             return name
         r = self.connection.ops.quote_name(name)
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index c29b08556f..4c60a3b09e 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -114,6 +114,10 @@ class Query(object):
         # type they are. The key is the alias of the joined table (possibly
         # the table name) and the value is JoinInfo from constants.py.
         self.alias_map = {}
+        # Sometimes the query contains references to aliases in outer queries (as
+        # a result of split_exclude). Correct alias quoting needs to know these
+        # aliases too.
+        self.external_aliases = set()
         self.table_map = {}     # Maps table names to list of aliases.
         self.join_map = {}
         self.default_cols = True
@@ -241,6 +245,7 @@ class Query(object):
         obj.model = self.model
         obj.alias_refcount = self.alias_refcount.copy()
         obj.alias_map = self.alias_map.copy()
+        obj.external_aliases = self.external_aliases.copy()
         obj.table_map = self.table_map.copy()
         obj.join_map = self.join_map.copy()
         obj.default_cols = self.default_cols
@@ -335,6 +340,11 @@ class Query(object):
             # Return value depends on the type of the field being processed.
             return self.convert_values(value, aggregate.field, connection)
 
+    def relabeled_clone(self, change_map):
+        clone = self.clone()
+        clone.change_aliases(change_map)
+        return clone
+
     def get_aggregation(self, using, force_subq=False):
         """
         Returns the dictionary with the values of the existing aggregations.
@@ -788,7 +798,9 @@ class Query(object):
             ident = (change_map.get(ident[0], ident[0]),) + ident[1:]
             self.join_map[ident] = aliases
         for old_alias, new_alias in six.iteritems(change_map):
-            alias_data = self.alias_map[old_alias]
+            alias_data = self.alias_map.get(old_alias)
+            if alias_data is None:
+                continue
             alias_data = alias_data._replace(rhs_alias=new_alias)
             self.alias_refcount[new_alias] = self.alias_refcount[old_alias]
             del self.alias_refcount[old_alias]
@@ -815,6 +827,9 @@ class Query(object):
                 data = data._replace(lhs_alias=change_map[lhs])
                 self.alias_map[alias] = data
 
+        self.external_aliases = {change_map.get(alias, alias)
+                                 for alias in self.external_aliases}
+
     def bump_prefix(self, outer_query):
         """
         Changes the alias prefix to the next letter in the alphabet in a way
@@ -1048,6 +1063,9 @@ class Query(object):
         elif isinstance(value, ExpressionNode):
             # If value is a query expression, evaluate it
             value = SQLEvaluator(value, self, reuse=can_reuse)
+        # Subqueries need to use a different set of aliases than the
+        # outer query. Call bump_prefix to change aliases of the inner
+        # query (the value).
         if hasattr(value, 'query') and hasattr(value.query, 'bump_prefix'):
             value = value._clone()
             value.query.bump_prefix(self)
@@ -1509,6 +1527,7 @@ class Query(object):
             lookup = lookup_class(Col(query.select[0].col[0], pk, pk),
                                   Col(alias, pk, pk))
             query.where.add(lookup, AND)
+            query.external_aliases.add(alias)
 
         condition, needed_inner = self.build_filter(
             ('%s__in' % trimmed_prefix, query),
diff --git a/docs/releases/1.7.2.txt b/docs/releases/1.7.2.txt
index 8af832d1a5..cfa68b8b3a 100644
--- a/docs/releases/1.7.2.txt
+++ b/docs/releases/1.7.2.txt
@@ -71,3 +71,6 @@ Bugfixes
 
 * Avoided unnecessary rollbacks of migrations from other apps when migrating
   backwards (:ticket:`23410`).
+
+* Fixed a rare query error when using deeply nested subqueries
+  (:ticket:`23605`).
diff --git a/tests/queries/models.py b/tests/queries/models.py
index 604eed5f07..6e6a0ce5e1 100644
--- a/tests/queries/models.py
+++ b/tests/queries/models.py
@@ -675,3 +675,18 @@ class Student(models.Model):
 class Classroom(models.Model):
     school = models.ForeignKey(School)
     students = models.ManyToManyField(Student, related_name='classroom')
+
+
+class Ticket23605A(models.Model):
+    pass
+
+
+class Ticket23605B(models.Model):
+    modela_fk = models.ForeignKey(Ticket23605A)
+    modelc_fk = models.ForeignKey("Ticket23605C")
+    field_b0 = models.IntegerField(null=True)
+    field_b1 = models.BooleanField(default=False)
+
+
+class Ticket23605C(models.Model):
+    field_c0 = models.FloatField()
diff --git a/tests/queries/tests.py b/tests/queries/tests.py
index 0fff68b21f..f6162508b9 100644
--- a/tests/queries/tests.py
+++ b/tests/queries/tests.py
@@ -27,7 +27,8 @@ from .models import (
     BaseA, FK1, Identifier, Program, Channel, Page, Paragraph, Chapter, Book,
     MyObject, Order, OrderItem, SharedConnection, Task, Staff, StaffUser,
     CategoryRelationship, Ticket21203Parent, Ticket21203Child, Person,
-    Company, Employment, CustomPk, CustomPkTag, Classroom, School, Student)
+    Company, Employment, CustomPk, CustomPkTag, Classroom, School, Student,
+    Ticket23605A, Ticket23605B, Ticket23605C)
 
 
 class BaseQuerysetTest(TestCase):
@@ -3391,3 +3392,39 @@ class Ticket22429Tests(TestCase):
 
         queryset = Student.objects.filter(~Q(classroom__school=F('school')))
         self.assertQuerysetEqual(queryset, [st2], lambda x: x)
+
+
+class Ticket23605Tests(TestCase):
+    def test_ticket_23605(self):
+        # Test filtering on a complicated q-object from ticket's report.
+        # The query structure is such that we have multiple nested subqueries.
+        # The original problem was that the inner queries weren't relabeled
+        # correctly.
+        a1 = Ticket23605A.objects.create()
+        a2 = Ticket23605A.objects.create()
+        c1 = Ticket23605C.objects.create(field_c0=10000.0)
+        Ticket23605B.objects.create(
+            field_b0=10000.0, field_b1=True,
+            modelc_fk=c1, modela_fk=a1)
+        complex_q = Q(pk__in=Ticket23605A.objects.filter(
+            Q(
+                # True for a1 as field_b0 = 10000, field_c0=10000
+                # False for a2 as no ticket23605b found
+                ticket23605b__field_b0__gte=1000000 /
+                F("ticket23605b__modelc_fk__field_c0")
+            ) &
+            # True for a1 (field_b1=True)
+            Q(ticket23605b__field_b1=True) &
+            ~Q(ticket23605b__pk__in=Ticket23605B.objects.filter(
+                ~(
+                    # Same filters as above commented filters, but
+                    # double-negated (one for Q() above, one for
+                    # parentheses). So, again a1 match, a2 not.
+                    Q(field_b1=True) &
+                    Q(field_b0__gte=1000000 / F("modelc_fk__field_c0"))
+                )
+            ))).filter(ticket23605b__field_b1=True))
+        qs1 = Ticket23605A.objects.filter(complex_q)
+        self.assertQuerysetEqual(qs1, [a1], lambda x: x)
+        qs2 = Ticket23605A.objects.exclude(complex_q)
+        self.assertQuerysetEqual(qs2, [a2], lambda x: x)