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

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index 80d544068..22e24be84 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -3479,6 +3479,7 @@ class Query(Generative):
             kwargs.get("limit") is not None
             or kwargs.get("offset") is not None
             or kwargs.get("distinct", False)
+            or kwargs.get("group_by", False)
         )
 
     def exists(self):