Fixed #32632, Fixed #32657 -- Removed flawed support for Subquery deconstruction.

Subquery deconstruction support required implementing complex and
expensive equality rules for sql.Query objects for little benefit as
the latter cannot themselves be made deconstructible to their reference
to model classes.

Making Expression @deconstructible and not BaseExpression allows
interested parties to conform to the "expression" API even if they are
not deconstructible as it's only a requirement for expressions allowed
in Model fields and meta options (e.g. constraints, indexes).

Thanks Phillip Cutter for the report.

This also fixes a performance regression in bbf141bcdc31f1324048af9233583a523ac54c94.

2 files changed, 15 insertions, 32 deletions

diff --git a/tests/queries/test_q.py b/tests/queries/test_q.py
index 84ae6e90a5..bd39b2dc32 100644
--- a/tests/queries/test_q.py
+++ b/tests/queries/test_q.py
@@ -1,4 +1,5 @@
-from django.db.models import Exists, F, OuterRef, Q
+from django.db.models import BooleanField, Exists, F, OuterRef, Q
+from django.db.models.expressions import RawSQL
 from django.test import SimpleTestCase
 
 from .models import Tag
@@ -50,6 +51,16 @@ class QTests(SimpleTestCase):
         with self.assertRaisesMessage(TypeError, str(obj)):
             q & obj
 
+    def test_combine_negated_boolean_expression(self):
+        tagged = Tag.objects.filter(category=OuterRef('pk'))
+        tests = [
+            Q() & ~Exists(tagged),
+            Q() | ~Exists(tagged),
+        ]
+        for q in tests:
+            with self.subTest(q=q):
+                self.assertIs(q.negated, True)
+
     def test_deconstruct(self):
         q = Q(price__gt=F('discounted_price'))
         path, args, kwargs = q.deconstruct()
@@ -101,10 +112,10 @@ class QTests(SimpleTestCase):
         self.assertEqual(kwargs, {})
 
     def test_deconstruct_boolean_expression(self):
-        tagged = Tag.objects.filter(category=OuterRef('pk'))
-        q = Q(Exists(tagged))
+        expr = RawSQL('1 = 1', BooleanField())
+        q = Q(expr)
         _, args, kwargs = q.deconstruct()
-        self.assertEqual(args, (Exists(tagged),))
+        self.assertEqual(args, (expr,))
         self.assertEqual(kwargs, {})
 
     def test_reconstruct(self):
diff --git a/tests/queries/test_query.py b/tests/queries/test_query.py
index 5db9d96163..523fa607f0 100644
--- a/tests/queries/test_query.py
+++ b/tests/queries/test_query.py
@@ -150,31 +150,3 @@ class TestQuery(SimpleTestCase):
         msg = 'Cannot filter against a non-conditional expression.'
         with self.assertRaisesMessage(TypeError, msg):
             query.build_where(Func(output_field=CharField()))
-
-    def test_equality(self):
-        self.assertNotEqual(
-            Author.objects.all().query,
-            Author.objects.filter(item__name='foo').query,
-        )
-        self.assertEqual(
-            Author.objects.filter(item__name='foo').query,
-            Author.objects.filter(item__name='foo').query,
-        )
-        self.assertEqual(
-            Author.objects.filter(item__name='foo').query,
-            Author.objects.filter(Q(item__name='foo')).query,
-        )
-
-    def test_hash(self):
-        self.assertNotEqual(
-            hash(Author.objects.all().query),
-            hash(Author.objects.filter(item__name='foo').query)
-        )
-        self.assertEqual(
-            hash(Author.objects.filter(item__name='foo').query),
-            hash(Author.objects.filter(item__name='foo').query),
-        )
-        self.assertEqual(
-            hash(Author.objects.filter(item__name='foo').query),
-            hash(Author.objects.filter(Q(item__name='foo')).query),
-        )