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

Thanks Jacob Walls for the review.

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

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} "

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)

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"

docs/ref/models/fields.txt

@@ -1346,8 +1346,13 @@ materialized view.
     real column. If ``False``, the column acts as a virtual column and does
     not occupy database storage space.
 
-    PostgreSQL < 18 only supports persisted columns. Oracle only supports
-    virtual columns.
+    PostgreSQL < 18 only supports persisted columns. Oracle < 23ai/26ai (23.7)
+    only supports virtual columns.
+
+    .. versionchanged:: 6.1
+
+        Support for stored ``GeneratedField``\s was added on Oracle 23ai/26ai
+        (23.7+).
 
 .. admonition:: Database limitations
 

docs/releases/6.1.txt

@@ -266,6 +266,10 @@ Models
 * The new :class:`~django.db.models.functions.UUID4` and
   :class:`~django.db.models.functions.UUID7` database functions were added.
 
+* :class:`~django.db.models.GeneratedField` now supports stored columns
+  (:attr:`~django.db.models.GeneratedField.db_persist` set to ``True``) on
+  Oracle 23ai/26ai (23.7+).
+
 Pagination
 ~~~~~~~~~~
 

tests/migrations/test_operations.py

@@ -1491,7 +1491,7 @@ class OperationTests(OperationTestBase):
                             "name_and_id",
                             models.GeneratedField(
                                 expression=Concat(("name"), ("rider_id")),
-                                output_field=models.TextField(),
+                                output_field=models.CharField(max_length=60),
                                 db_persist=True,
                             ),
                         ),
@@ -6363,6 +6363,15 @@ class OperationTests(OperationTestBase):
             ("test_igfc_2", generated_1, regular),
             ("test_igfc_3", generated_1, generated_2),
         ]
+        if not connection.features.supports_alter_generated_column_data_type:
+            generated_3 = models.GeneratedField(
+                expression=F("pink") + F("pink"),
+                output_field=models.DecimalField(decimal_places=2, max_digits=16),
+                db_persist=db_persist,
+            )
+            tests.append(
+                ("test_igfc_4", generated_1, generated_3),
+            )
         for app_label, add_field, alter_field in tests:
             project_state = self.set_up_test_model(app_label)
             operations = [
@@ -6441,7 +6450,7 @@ class OperationTests(OperationTestBase):
                 "Pony",
                 "modified_pink",
                 models.GeneratedField(
-                    expression=F("pink"),
+                    expression=F("pink") + 2,
                     output_field=models.IntegerField(),
                     db_persist=True,
                 ),
@@ -6450,7 +6459,7 @@ class OperationTests(OperationTestBase):
                 "Pony",
                 "modified_pink",
                 models.GeneratedField(
-                    expression=F("pink"),
+                    expression=F("pink") + 2,
                     output_field=models.IntegerField(),
                     db_persist=False,
                 ),
@@ -6489,7 +6498,9 @@ class OperationTests(OperationTestBase):
             operation.database_backwards(app_label, editor, new_state, project_state)
         self.assertColumnNotExists(f"{app_label}_pony", "modified_pink")
 
-    @skipUnlessDBFeature("supports_stored_generated_columns")
+    @skipUnlessDBFeature(
+        "supports_stored_generated_columns", "supports_alter_generated_column_data_type"
+    )
     def test_generated_field_changes_output_field(self):
         app_label = "test_gfcof"
         operation = migrations.AddField(

tests/model_fields/models.py

@@ -9,7 +9,7 @@ from django.core.serializers.json import DjangoJSONEncoder
 from django.db import connection, models
 from django.db.models import F, Value
 from django.db.models.fields.files import ImageFieldFile
-from django.db.models.functions import Lower
+from django.db.models.functions import Cast, Lower
 from django.utils.functional import SimpleLazyObject
 from django.utils.translation import gettext_lazy as _
 
@@ -534,7 +534,7 @@ class UUIDGrandchild(UUIDChild):
 class GeneratedModelFieldWithConverters(models.Model):
     field = models.UUIDField()
     field_copy = models.GeneratedField(
-        expression=F("field"),
+        expression=Cast("field", models.UUIDField()),
         output_field=models.UUIDField(),
         db_persist=True,
     )
@@ -561,7 +561,7 @@ class GeneratedModelNonAutoPk(models.Model):
     id = models.IntegerField(primary_key=True)
     a = models.IntegerField()
     b = models.GeneratedField(
-        expression=F("a"),
+        expression=F("a") + 1,
         output_field=models.IntegerField(),
         db_persist=True,
     )

tests/model_fields/test_generatedfield.py

@@ -413,7 +413,7 @@ class StoredGeneratedFieldTests(GeneratedFieldTestMixin, TestCase):
         obj = GeneratedModelNonAutoPk.objects.create(id=1, a=2)
         self.assertEqual(obj.id, 1)
         self.assertEqual(obj.a, 2)
-        self.assertEqual(obj.b, 2)
+        self.assertEqual(obj.b, 3)
 
 
 @skipUnlessDBFeature("supports_virtual_generated_columns")

tests/schema/tests.py

@@ -1029,7 +1029,7 @@ class SchemaTests(TransactionTestCase):
         class GeneratedFieldIndexedModel(Model):
             number = IntegerField(default=1)
             generated = GeneratedField(
-                expression=F("number"),
+                expression=F("number") + 1,
                 db_persist=True,
                 output_field=IntegerField(),
             )
@@ -1042,7 +1042,7 @@ class SchemaTests(TransactionTestCase):
 
         old_field = GeneratedFieldIndexedModel._meta.get_field("generated")
         new_field = GeneratedField(
-            expression=F("number"),
+            expression=F("number") + 1,
             db_persist=True,
             db_index=True,
             output_field=IntegerField(),