Fixed #36718 -- Added JSONField support for negative array indexing on Oracle 21c+.

Author: cliffordgama

django/db/backends/oracle/features.py

@@ -76,7 +76,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     requires_compound_order_by_subquery = True
     allows_multiple_constraints_on_same_fields = False
     supports_json_field_contains = False
-    supports_json_negative_indexing = False
     supports_collation_on_textfield = False
     supports_on_delete_db_default = False
     supports_no_precision_decimalfield = True
@@ -91,6 +90,10 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         "INSERT INTO {} VALUES (DEFAULT, DEFAULT, DEFAULT)"
     )
 
+    @cached_property
+    def supports_json_negative_indexing(self):
+        return self.connection.oracle_version >= (21,)
+
     @cached_property
     def django_test_skips(self):
         skips = {

django/db/backends/oracle/operations.py

@@ -729,3 +729,8 @@ def conditional_expression_supported_in_where_clause(self, expression):
         if isinstance(expression, RawSQL) and expression.conditional:
             return True
         return False
+
+    def format_json_path_numeric_index(self, num):
+        if num < 0:
+            return "[last-%s]" % abs(num + 1)  # Indexing is zero-based.
+        return super().format_json_path_numeric_index(num)

docs/releases/6.1.txt

@@ -254,6 +254,10 @@ Models
   <django.db.models.DecimalField.decimal_places>` are no longer required to be
   set on Oracle, PostgreSQL, and SQLite.
 
+* :class:`~django.db.models.JSONField` now supports
+  :ref:`negative array indexing <key-index-and-path-transforms>` on Oracle
+  21c+.
+
 Pagination
 ~~~~~~~~~~
 

docs/topics/db/queries.txt

@@ -1184,14 +1184,18 @@ directly, but you can still use dictionary unpacking to use it in a query:
     >>> Dog.objects.filter(**{"data__owner__other_pets__-1__name": "Fishy"})
     <QuerySet [<Dog: Rufus>]>
 
-.. admonition:: MySQL, MariaDB, and Oracle
+.. admonition:: MySQL, MariaDB, and Oracle < 21c
 
     Negative JSON array indices are not supported.
 
 .. versionchanged:: 6.0
 
     SQLite support for negative JSON array indices was added.
 
+.. versionchanged:: 6.1
+
+    Oracle 21c+ support for negative JSON array indices was added.
+
 If the key you wish to query by clashes with the name of another lookup, use
 the :lookup:`contains <jsonfield.contains>` lookup instead.