Fixed #30027 -- Errored out on Window function usage if unsupported.

1 files changed, 3 insertions, 0 deletions

diff --git a/django/db/models/expressions.py b/django/db/models/expressions.py
index 6afe68bac0..ccb67876e2 100644
--- a/django/db/models/expressions.py
+++ b/django/db/models/expressions.py
@@ -7,6 +7,7 @@ from django.core.exceptions import EmptyResultSet, FieldError
 from django.db import connection
 from django.db.models import fields
 from django.db.models.query_utils import Q
+from django.db.utils import NotSupportedError
 from django.utils.deconstruct import deconstructible
 from django.utils.functional import cached_property
 from django.utils.hashable import make_hashable
@@ -1237,6 +1238,8 @@ class Window(Expression):
 
     def as_sql(self, compiler, connection, template=None):
         connection.ops.check_expression_support(self)
+        if not connection.features.supports_over_clause:
+            raise NotSupportedError('This backend does not support window expressions.')
         expr_sql, params = compiler.compile(self.source_expression)
         window_sql, window_params = [], []