[3.1.x] Fixed #31751 -- Fixed database introspection with cx_Oracle 8.

Backport of 615e32162f from master

django/contrib/gis/db/backends/oracle/introspection.py

@@ -1,14 +1,19 @@
 import cx_Oracle
 
 from django.db.backends.oracle.introspection import DatabaseIntrospection
+from django.utils.functional import cached_property
 
 
 class OracleIntrospection(DatabaseIntrospection):
     # Associating any OBJECTVAR instances with GeometryField. This won't work
     # right on Oracle objects that aren't MDSYS.SDO_GEOMETRY, but it is the
     # only object type supported within Django anyways.
-    data_types_reverse = DatabaseIntrospection.data_types_reverse.copy()
-    data_types_reverse[cx_Oracle.OBJECT] = 'GeometryField'
+    @cached_property
+    def data_types_reverse(self):
+        return {
+            **super().data_types_reverse,
+            cx_Oracle.OBJECT: 'GeometryField',
+        }
 
     def get_geometry_type(self, table_name, description):
         with self.connection.cursor() as cursor:

django/db/backends/oracle/base.py

@@ -323,6 +323,10 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         else:
             return True
 
+    @cached_property
+    def cx_oracle_version(self):
+        return tuple(int(x) for x in Database.version.split('.'))
+
     @cached_property
     def oracle_version(self):
         with self.temporary_connection():

django/db/backends/oracle/introspection.py

@@ -6,29 +6,48 @@ from django.db import models
 from django.db.backends.base.introspection import (
     BaseDatabaseIntrospection, FieldInfo as BaseFieldInfo, TableInfo,
 )
+from django.utils.functional import cached_property
 
 FieldInfo = namedtuple('FieldInfo', BaseFieldInfo._fields + ('is_autofield', 'is_json'))
 
 
 class DatabaseIntrospection(BaseDatabaseIntrospection):
-    # Maps type objects to Django Field types.
-    data_types_reverse = {
-        cx_Oracle.BLOB: 'BinaryField',
-        cx_Oracle.CLOB: 'TextField',
-        cx_Oracle.DATETIME: 'DateField',
-        cx_Oracle.FIXED_CHAR: 'CharField',
-        cx_Oracle.FIXED_NCHAR: 'CharField',
-        cx_Oracle.INTERVAL: 'DurationField',
-        cx_Oracle.NATIVE_FLOAT: 'FloatField',
-        cx_Oracle.NCHAR: 'CharField',
-        cx_Oracle.NCLOB: 'TextField',
-        cx_Oracle.NUMBER: 'DecimalField',
-        cx_Oracle.STRING: 'CharField',
-        cx_Oracle.TIMESTAMP: 'DateTimeField',
-    }
-
     cache_bust_counter = 1
 
+    # Maps type objects to Django Field types.
+    @cached_property
+    def data_types_reverse(self):
+        if self.connection.cx_oracle_version < (8,):
+            return {
+                cx_Oracle.BLOB: 'BinaryField',
+                cx_Oracle.CLOB: 'TextField',
+                cx_Oracle.DATETIME: 'DateField',
+                cx_Oracle.FIXED_CHAR: 'CharField',
+                cx_Oracle.FIXED_NCHAR: 'CharField',
+                cx_Oracle.INTERVAL: 'DurationField',
+                cx_Oracle.NATIVE_FLOAT: 'FloatField',
+                cx_Oracle.NCHAR: 'CharField',
+                cx_Oracle.NCLOB: 'TextField',
+                cx_Oracle.NUMBER: 'DecimalField',
+                cx_Oracle.STRING: 'CharField',
+                cx_Oracle.TIMESTAMP: 'DateTimeField',
+            }
+        else:
+            return {
+                cx_Oracle.DB_TYPE_DATE: 'DateField',
+                cx_Oracle.DB_TYPE_BINARY_DOUBLE: 'FloatField',
+                cx_Oracle.DB_TYPE_BLOB: 'BinaryField',
+                cx_Oracle.DB_TYPE_CHAR: 'CharField',
+                cx_Oracle.DB_TYPE_CLOB: 'TextField',
+                cx_Oracle.DB_TYPE_INTERVAL_DS: 'DurationField',
+                cx_Oracle.DB_TYPE_NCHAR: 'CharField',
+                cx_Oracle.DB_TYPE_NCLOB: 'TextField',
+                cx_Oracle.DB_TYPE_NVARCHAR: 'CharField',
+                cx_Oracle.DB_TYPE_NUMBER: 'DecimalField',
+                cx_Oracle.DB_TYPE_TIMESTAMP: 'DateTimeField',
+                cx_Oracle.DB_TYPE_VARCHAR: 'CharField',
+            }
+
     def get_field_type(self, data_type, description):
         if data_type == cx_Oracle.NUMBER:
             precision, scale = description[4:6]

docs/releases/3.0.8.txt

@@ -22,3 +22,5 @@ Bugfixes
 * Fixed a regression in Django 3.0.2 that caused a migration crash on
   PostgreSQL when adding a foreign key to a model with a namespaced
   ``db_table`` (:ticket:`31735`).
+
+* Added compatibility for ``cx_Oracle`` 8 (:ticket:`31751`).