[1.6.x] Fixed #21748 -- join promotion for negated AND conditions

Made sure Django treats case .filter(NOT (a AND b)) the same way as
.filter((NOT a OR NOT b)) for join promotion.

Heavily modified backpatch of 35cecb1ebd
from master.

Conflicts:

	django/db/models/sql/query.py
	tests/queries/tests.py

django/db/models/sql/query.py

@@ -1211,16 +1211,18 @@ class Query(object):
         connector = q_object.connector
         current_negated = current_negated ^ q_object.negated
         branch_negated = branch_negated or q_object.negated
-        # Note that if the connector happens to match what we have already in
-        # the tree, the add will be a no-op.
         target_clause = self.where_class(connector=connector,
                                          negated=q_object.negated)
-
+        # Treat case NOT (a AND b) like case ((NOT a) OR (NOT b)) for join
-        if connector == OR:
+        # promotion. See ticket #21748.
+        effective_connector = connector
+        if current_negated:
+            effective_connector = OR if effective_connector == AND else AND
+        if effective_connector == OR:
             alias_usage_counts = dict()
             aliases_before = set(self.tables)
         for child in q_object.children:
-            if connector == OR:
+            if effective_connector == OR:
                 refcounts_before = self.alias_refcount.copy()
             if isinstance(child, Node):
                 child_clause = self._add_q(
@@ -1231,11 +1233,11 @@ class Query(object):
                     child, can_reuse=used_aliases, branch_negated=branch_negated,
                     current_negated=current_negated)
             target_clause.add(child_clause, connector)
-            if connector == OR:
+            if effective_connector == OR:
                 used = alias_diff(refcounts_before, self.alias_refcount)
                 for alias in used:
                     alias_usage_counts[alias] = alias_usage_counts.get(alias, 0) + 1
-        if connector == OR:
+        if effective_connector == OR:
             self.promote_disjunction(aliases_before, alias_usage_counts,
                                      len(q_object.children))
         return target_clause

tests/queries/tests.py

@@ -2662,6 +2662,85 @@ class NullJoinPromotionOrTest(TestCase):
         self.assertEqual(str(qs.query).count('INNER JOIN'), 1)
         self.assertEqual(list(qs), [self.a2])
 
+    def test_ticket_21748(self):
+        i1 = Identifier.objects.create(name='i1')
+        i2 = Identifier.objects.create(name='i2')
+        i3 = Identifier.objects.create(name='i3')
+        Program.objects.create(identifier=i1)
+        Channel.objects.create(identifier=i1)
+        Program.objects.create(identifier=i2)
+        self.assertQuerysetEqual(
+            Identifier.objects.filter(program=None, channel=None),
+            [i3], lambda x: x)
+        self.assertQuerysetEqual(
+            Identifier.objects.exclude(program=None, channel=None).order_by('name'),
+            [i1, i2], lambda x: x)
+
+    def test_ticket_21748_double_negated_and(self):
+        i1 = Identifier.objects.create(name='i1')
+        i2 = Identifier.objects.create(name='i2')
+        Identifier.objects.create(name='i3')
+        p1 = Program.objects.create(identifier=i1)
+        c1 = Channel.objects.create(identifier=i1)
+        Program.objects.create(identifier=i2)
+        # Check the ~~Q() (or equivalently .exclude(~Q)) works like Q() for
+        # join promotion.
+        qs1_doubleneg = Identifier.objects.exclude(~Q(program__id=p1.id, channel__id=c1.id)).order_by('pk')
+        qs1_filter = Identifier.objects.filter(program__id=p1.id, channel__id=c1.id).order_by('pk')
+        self.assertQuerysetEqual(qs1_doubleneg, qs1_filter, lambda x: x)
+        self.assertEqual(str(qs1_filter.query).count('JOIN'),
+                         str(qs1_doubleneg.query).count('JOIN'))
+        self.assertEqual(2, str(qs1_doubleneg.query).count('INNER JOIN'))
+        self.assertEqual(str(qs1_filter.query).count('INNER JOIN'),
+                         str(qs1_doubleneg.query).count('INNER JOIN'))
+
+    def test_ticket_21748_double_negated_or(self):
+        i1 = Identifier.objects.create(name='i1')
+        i2 = Identifier.objects.create(name='i2')
+        Identifier.objects.create(name='i3')
+        p1 = Program.objects.create(identifier=i1)
+        c1 = Channel.objects.create(identifier=i1)
+        p2 = Program.objects.create(identifier=i2)
+        # Test OR + doubleneq. The expected result is that channel is LOUTER
+        # joined, program INNER joined
+        qs1_filter = Identifier.objects.filter(
+            Q(program__id=p2.id, channel__id=c1.id)
+            | Q(program__id=p1.id)
+        ).order_by('pk')
+        qs1_doubleneg = Identifier.objects.exclude(
+            ~Q(Q(program__id=p2.id, channel__id=c1.id)
+            | Q(program__id=p1.id))
+        ).order_by('pk')
+        self.assertQuerysetEqual(qs1_doubleneg, qs1_filter, lambda x: x)
+        self.assertEqual(str(qs1_filter.query).count('JOIN'),
+                         str(qs1_doubleneg.query).count('JOIN'))
+        self.assertEqual(1, str(qs1_doubleneg.query).count('INNER JOIN'))
+        self.assertEqual(str(qs1_filter.query).count('INNER JOIN'),
+                         str(qs1_doubleneg.query).count('INNER JOIN'))
+
+    def test_ticket_21748_complex_filter(self):
+        i1 = Identifier.objects.create(name='i1')
+        i2 = Identifier.objects.create(name='i2')
+        Identifier.objects.create(name='i3')
+        p1 = Program.objects.create(identifier=i1)
+        c1 = Channel.objects.create(identifier=i1)
+        p2 = Program.objects.create(identifier=i2)
+        # Finally, a more complex case, one time in a way where each
+        # NOT is pushed to lowest level in the boolean tree, and
+        # another query where this isn't done.
+        qs1 = Identifier.objects.filter(
+            ~Q(~Q(program__id=p2.id, channel__id=c1.id)
+            & Q(program__id=p1.id))).order_by('pk')
+        qs2 = Identifier.objects.filter(
+            Q(Q(program__id=p2.id, channel__id=c1.id)
+            | ~Q(program__id=p1.id))).order_by('pk')
+        self.assertQuerysetEqual(qs1, qs2, lambda x: x)
+        self.assertEqual(str(qs1.query).count('JOIN'),
+                         str(qs2.query).count('JOIN'))
+        self.assertEqual(0, str(qs1.query).count('INNER JOIN'))
+        self.assertEqual(str(qs1.query).count('INNER JOIN'),
+                         str(qs2.query).count('INNER JOIN'))
+
 
 class ReverseJoinTrimmingTest(TestCase):
     def test_reverse_trimming(self):