Fixed #36765 -- Added support for stored GeneratedFields on Oracle 23ai/26ai (23.7+).

Thanks Jacob Walls for the review.

4 files changed, 29 insertions, 2 deletions

diff --git a/django/db/backends/base/features.py b/django/db/backends/base/features.py
index a28d622bac..2031beaf8a 100644
--- a/django/db/backends/base/features.py
+++ b/django/db/backends/base/features.py
@@ -373,6 +373,8 @@ class BaseDatabaseFeatures:
     supports_stored_generated_columns = False
     # Does the backend support virtual generated columns?
     supports_virtual_generated_columns = False
+    # Does the backend support altering data types of generated columns?
+    supports_alter_generated_column_data_type = True
 
     # Does the backend support the logical XOR operator?
     supports_logical_xor = False
diff --git a/django/db/backends/base/schema.py b/django/db/backends/base/schema.py
index 1f27d6a0d4..4a59a6fe67 100644
--- a/django/db/backends/base/schema.py
+++ b/django/db/backends/base/schema.py
@@ -452,10 +452,14 @@ class BaseDatabaseSchemaEditor:
             params = []
         return sql % default_sql, params
 
+    def _column_generated_persistency_sql(self, field):
+        """Return the SQL to define the persistency of generated fields."""
+        return "STORED" if field.db_persist else "VIRTUAL"
+
     def _column_generated_sql(self, field):
         """Return the SQL to use in a GENERATED ALWAYS clause."""
         expression_sql, params = field.generated_sql(self.connection)
-        persistency_sql = "STORED" if field.db_persist else "VIRTUAL"
+        persistency_sql = self._column_generated_persistency_sql(field)
         if self.connection.features.requires_literal_defaults:
             expression_sql = expression_sql % tuple(self.quote_value(p) for p in params)
             params = ()
@@ -906,6 +910,15 @@ class BaseDatabaseSchemaEditor:
             else:
                 new_field_sql = new_field.generated_sql(self.connection)
                 modifying_generated_field = old_field_sql != new_field_sql
+                db_features = self.connection.features
+                # Some databases (e.g. Oracle) don't allow altering a data type
+                # for generated columns.
+                if (
+                    not modifying_generated_field
+                    and old_type != new_type
+                    and not db_features.supports_alter_generated_column_data_type
+                ):
+                    modifying_generated_field = True
         if modifying_generated_field:
             raise ValueError(
                 f"Modifying GeneratedFields is not supported - the field {new_field} "
diff --git a/django/db/backends/oracle/features.py b/django/db/backends/oracle/features.py
index 78dc97a2ec..ea484e336e 100644
--- a/django/db/backends/oracle/features.py
+++ b/django/db/backends/oracle/features.py
@@ -69,8 +69,8 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_ignore_conflicts = False
     max_query_params = 2**16 - 1
     supports_partial_indexes = False
-    supports_stored_generated_columns = False
     supports_virtual_generated_columns = True
+    supports_alter_generated_column_data_type = False
     can_rename_index = True
     supports_slicing_ordering_in_compound = True
     requires_compound_order_by_subquery = True
@@ -131,6 +131,11 @@ class DatabaseFeatures(BaseDatabaseFeatures):
             "Oracle doesn't support casting filters to NUMBER.": {
                 "lookup.tests.LookupQueryingTests.test_aggregate_combined_lookup",
             },
+            "Oracle doesn't support some data types (e.g. BOOLEAN, BLOB) in "
+            "GeneratedField expressions (ORA-54003).": {
+                "schema.tests.SchemaTests.test_add_generated_field_contains",
+                "schema.tests.SchemaTests.test_add_generated_field_with_kt_model",
+            },
         }
         if self.connection.oracle_version < (23,):
             skips.update(
@@ -228,3 +233,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     @cached_property
     def supports_uuid4_function(self):
         return self.connection.oracle_version >= (23, 9)
+
+    @cached_property
+    def supports_stored_generated_columns(self):
+        return self.connection.oracle_version >= (23, 7)
diff --git a/django/db/backends/oracle/schema.py b/django/db/backends/oracle/schema.py
index 13fa7220ce..2f79489631 100644
--- a/django/db/backends/oracle/schema.py
+++ b/django/db/backends/oracle/schema.py
@@ -251,3 +251,6 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
         if collation is None and old_collation is not None:
             collation = self._get_default_collation(table_name)
         return super()._collate_sql(collation, old_collation, table_name)
+
+    def _column_generated_persistency_sql(self, field):
+        return "MATERIALIZED" if field.db_persist else "VIRTUAL"