Refs #27149 -- Fixed sql.Query identity.

By making Query subclass BaseExpression in
35431298226165986ad07e91f9d3aca721ff38ec the former defined it's
identity based off _construct_args which is not appropriate.

5 files changed, 106 insertions, 13 deletions

diff --git a/django/db/models/lookups.py b/django/db/models/lookups.py
index 576ff400c4..43f40c24ec 100644
--- a/django/db/models/lookups.py
+++ b/django/db/models/lookups.py
@@ -12,6 +12,7 @@ from django.db.models.query_utils import RegisterLookupMixin
 from django.utils.datastructures import OrderedSet
 from django.utils.deprecation import RemovedInDjango40Warning
 from django.utils.functional import cached_property
+from django.utils.hashable import make_hashable
 
 
 class Lookup:
@@ -143,6 +144,18 @@ class Lookup:
     def is_summary(self):
         return self.lhs.is_summary or getattr(self.rhs, 'is_summary', False)
 
+    @property
+    def identity(self):
+        return self.__class__, self.lhs, self.rhs
+
+    def __eq__(self, other):
+        if not isinstance(other, Lookup):
+            return NotImplemented
+        return self.identity == other.identity
+
+    def __hash__(self):
+        return hash(make_hashable(self.identity))
+
 
 class Transform(RegisterLookupMixin, Func):
     """
diff --git a/django/db/models/sql/datastructures.py b/django/db/models/sql/datastructures.py
index c2c347b3cf..c9598b3bd4 100644
--- a/django/db/models/sql/datastructures.py
+++ b/django/db/models/sql/datastructures.py
@@ -114,17 +114,28 @@ class Join:
             self.join_field, self.nullable, filtered_relation=filtered_relation,
         )
 
-    def equals(self, other, with_filtered_relation):
+    @property
+    def identity(self):
         return (
-            isinstance(other, self.__class__) and
-            self.table_name == other.table_name and
-            self.parent_alias == other.parent_alias and
-            self.join_field == other.join_field and
-            (not with_filtered_relation or self.filtered_relation == other.filtered_relation)
+            self.__class__,
+            self.table_name,
+            self.parent_alias,
+            self.join_field,
+            self.filtered_relation,
         )
 
     def __eq__(self, other):
-        return self.equals(other, with_filtered_relation=True)
+        if not isinstance(other, Join):
+            return NotImplemented
+        return self.identity == other.identity
+
+    def __hash__(self):
+        return hash(self.identity)
+
+    def equals(self, other, with_filtered_relation):
+        if with_filtered_relation:
+            return self == other
+        return self.identity[:-1] == other.identity[:-1]
 
     def demote(self):
         new = self.relabeled_clone({})
@@ -160,9 +171,17 @@ class BaseTable:
     def relabeled_clone(self, change_map):
         return self.__class__(self.table_name, change_map.get(self.table_alias, self.table_alias))
 
+    @property
+    def identity(self):
+        return self.__class__, self.table_name, self.table_alias
+
+    def __eq__(self, other):
+        if not isinstance(other, BaseTable):
+            return NotImplemented
+        return self.identity == other.identity
+
+    def __hash__(self):
+        return hash(self.identity)
+
     def equals(self, other, with_filtered_relation):
-        return (
-            isinstance(self, other.__class__) and
-            self.table_name == other.table_name and
-            self.table_alias == other.table_alias
-        )
+        return self.identity == other.identity
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index ee98984826..8d76b436ee 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -39,6 +39,7 @@ from django.db.models.sql.where import (
 )
 from django.utils.deprecation import RemovedInDjango40Warning
 from django.utils.functional import cached_property
+from django.utils.hashable import make_hashable
 from django.utils.tree import Node
 
 __all__ = ['Query', 'RawQuery']
@@ -246,6 +247,14 @@ class Query(BaseExpression):
         for alias in self.alias_map:
             return alias
 
+    @property
+    def identity(self):
+        identity = (
+            (arg, make_hashable(value))
+            for arg, value in self.__dict__.items()
+        )
+        return (self.__class__, *identity)
+
     def __str__(self):
         """
         Return the query as a string of SQL with the parameter values
diff --git a/tests/lookup/test_lookups.py b/tests/lookup/test_lookups.py
index c3aa48ddad..4d90612048 100644
--- a/tests/lookup/test_lookups.py
+++ b/tests/lookup/test_lookups.py
@@ -1,10 +1,34 @@
 from datetime import datetime
+from unittest import mock
 
 from django.db.models import DateTimeField, Value
-from django.db.models.lookups import YearLookup
+from django.db.models.lookups import Lookup, YearLookup
 from django.test import SimpleTestCase
 
 
+class CustomLookup(Lookup):
+    pass
+
+
+class LookupTests(SimpleTestCase):
+    def test_equality(self):
+        lookup = Lookup(Value(1), Value(2))
+        self.assertEqual(lookup, lookup)
+        self.assertEqual(lookup, Lookup(lookup.lhs, lookup.rhs))
+        self.assertEqual(lookup, mock.ANY)
+        self.assertNotEqual(lookup, Lookup(lookup.lhs, Value(3)))
+        self.assertNotEqual(lookup, Lookup(Value(3), lookup.rhs))
+        self.assertNotEqual(lookup, CustomLookup(lookup.lhs, lookup.rhs))
+
+    def test_hash(self):
+        lookup = Lookup(Value(1), Value(2))
+        self.assertEqual(hash(lookup), hash(lookup))
+        self.assertEqual(hash(lookup), hash(Lookup(lookup.lhs, lookup.rhs)))
+        self.assertNotEqual(hash(lookup), hash(Lookup(lookup.lhs, Value(3))))
+        self.assertNotEqual(hash(lookup), hash(Lookup(Value(3), lookup.rhs)))
+        self.assertNotEqual(hash(lookup), hash(CustomLookup(lookup.lhs, lookup.rhs)))
+
+
 class YearLookupTests(SimpleTestCase):
     def test_get_bound_params(self):
         look_up = YearLookup(
diff --git a/tests/queries/test_query.py b/tests/queries/test_query.py
index 523fa607f0..5db9d96163 100644
--- a/tests/queries/test_query.py
+++ b/tests/queries/test_query.py
@@ -150,3 +150,31 @@ 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),
+        )