From 2c71a8d17df6671fa0cde33d643c993a4317536d Mon Sep 17 00:00:00 2001
From: Lumir Balhar <lbalhar@redhat.com>
Date: Mon, 4 Dec 2023 13:33:29 +0100
Subject: [PATCH] Include GROUP BY in _should_nest_selectable criteria

Fixed bug where usage of joined eager loading would not properly wrap the
query inside of a subquery when :meth:`.Query.group_by` were used against
the query.   When any kind of result-limiting approach is used, such as
DISTINCT, LIMIT, OFFSET, joined eager loading embeds the row-limited query
inside of a subquery so that the collection results are not impacted.   For
some reason, the presence of GROUP BY was never included in this criterion,
even though it has a similar effect as using DISTINCT.   Additionally, the
bug would prevent using GROUP BY at all for a joined eager load query for
most database platforms which forbid non-aggregated, non-grouped columns
from being in the query, as the additional columns for the joined eager
load would not be accepted by the database.

Fixes: #5065
Change-Id: I9a2ed8196f83297ec38012138d1a5acdf9e88155
---
 lib/sqlalchemy/orm/query.py         |  3 ++-
 test/orm/test_eager_relations.py    | 40 +++++++++++++++++++++++++++++
 test/orm/test_subquery_relations.py | 39 ++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index a17f590..bd0081f 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -3076,7 +3076,8 @@ class Query(object):
         kwargs = self._select_args
         return (kwargs.get('limit') is not None or
                 kwargs.get('offset') is not None or
-                kwargs.get('distinct', False))
+                kwargs.get('distinct', False) or
+                kwargs.get("group_by", False))
 
     def exists(self):
         """A convenience method that turns a query into an EXISTS subquery
diff --git a/test/orm/test_eager_relations.py b/test/orm/test_eager_relations.py
index 3c669d9..9aeeca5 100644
--- a/test/orm/test_eager_relations.py
+++ b/test/orm/test_eager_relations.py
@@ -747,6 +747,46 @@ class EagerTest(_fixtures.FixtureTest, testing.AssertsCompiledSQL):
             eq_(self.static.user_address_result, result)
         self.assert_sql_count(testing.db, go, 1)
 
+    def test_group_by_only(self):
+        # like distinct(), a group_by() has a similar effect so the
+        # joined eager load needs to subquery for this as well
+        users, Address, addresses, User = (
+            self.tables.users,
+            self.classes.Address,
+            self.tables.addresses,
+            self.classes.User,
+        )
+
+        mapper(
+            User,
+            users,
+            properties={
+                "addresses": relationship(
+                    mapper(Address, addresses),
+                    lazy="joined",
+                    order_by=addresses.c.email_address,
+                )
+            },
+        )
+
+        q = create_session().query(User)
+        eq_(
+            [
+                User(id=7, addresses=[Address(id=1)]),
+                User(
+                    id=8,
+                    addresses=[
+                        Address(id=3, email_address="ed@bettyboop.com"),
+                        Address(id=4, email_address="ed@lala.com"),
+                        Address(id=2, email_address="ed@wood.com"),
+                    ],
+                ),
+                User(id=9, addresses=[Address(id=5)]),
+                User(id=10, addresses=[]),
+            ],
+            q.order_by(User.id).group_by(User).all(),  # group by all columns
+        )
+
     def test_limit_2(self):
         keywords, items, item_keywords, Keyword, Item = (
             self.tables.keywords,
diff --git a/test/orm/test_subquery_relations.py b/test/orm/test_subquery_relations.py
index 606beb5..aef9c34 100644
--- a/test/orm/test_subquery_relations.py
+++ b/test/orm/test_subquery_relations.py
@@ -754,6 +754,45 @@ class EagerTest(_fixtures.FixtureTest, testing.AssertsCompiledSQL):
         result = q.limit(2).all()
         eq_(result, list(reversed(self.static.user_address_result[2:4])))
 
+    def test_group_by_only(self):
+        # test group_by() not impacting results, similarly to joinedload
+        users, Address, addresses, User = (
+            self.tables.users,
+            self.classes.Address,
+            self.tables.addresses,
+            self.classes.User,
+        )
+
+        mapper(
+            User,
+            users,
+            properties={
+                "addresses": relationship(
+                    mapper(Address, addresses),
+                    lazy="subquery",
+                    order_by=addresses.c.email_address,
+                )
+            },
+        )
+
+        q = create_session().query(User)
+        eq_(
+            [
+                User(id=7, addresses=[Address(id=1)]),
+                User(
+                    id=8,
+                    addresses=[
+                        Address(id=3, email_address="ed@bettyboop.com"),
+                        Address(id=4, email_address="ed@lala.com"),
+                        Address(id=2, email_address="ed@wood.com"),
+                    ],
+                ),
+                User(id=9, addresses=[Address(id=5)]),
+                User(id=10, addresses=[]),
+            ],
+            q.order_by(User.id).group_by(User).all(),  # group by all columns
+        )
+
     def test_one_to_many_scalar(self):
         Address, addresses, users, User = (self.classes.Address,
                                            self.tables.addresses,
-- 
2.43.0