Refs #24245 -- Added introspection for database defaults on Oracle.

django/db/backends/base/introspection.py

@@ -4,7 +4,7 @@ from collections import namedtuple
 TableInfo = namedtuple('TableInfo', ['name', 'type'])
 
 # Structure returned by the DB-API cursor.description interface (PEP 249)
-FieldInfo = namedtuple('FieldInfo', 'name type_code display_size internal_size precision scale null_ok')
+FieldInfo = namedtuple('FieldInfo', 'name type_code display_size internal_size precision scale null_ok default')
 
 
 class BaseDatabaseIntrospection(object):

django/db/backends/mysql/introspection.py

@@ -10,7 +10,7 @@ from django.utils.datastructures import OrderedSet
 from django.utils.deprecation import RemovedInDjango21Warning
 from django.utils.encoding import force_text
 
-FieldInfo = namedtuple('FieldInfo', FieldInfo._fields + ('extra', 'default'))
+FieldInfo = namedtuple('FieldInfo', FieldInfo._fields + ('extra',))
 InfoLine = namedtuple('InfoLine', 'col_name data_type max_len num_prec num_scale extra column_default')
 
 
@@ -89,8 +89,8 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
                         to_int(field_info[col_name].num_prec) or line[4],
                         to_int(field_info[col_name].num_scale) or line[5],
                         line[6],
-                        field_info[col_name].extra,
                         field_info[col_name].column_default,
+                        field_info[col_name].extra,
                     )
                 ))
             )

django/db/backends/oracle/features.py

@@ -22,7 +22,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     has_bulk_insert = True
     supports_tablespaces = True
     supports_sequence_reset = False
-    can_introspect_default = False  # Pending implementation by an interested person.
     can_introspect_max_length = False
     can_introspect_time_field = False
     atomic_transactions = False

django/db/backends/oracle/introspection.py

@@ -60,6 +60,13 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
 
     def get_table_description(self, cursor, table_name):
         "Returns a description of the table, with the DB-API cursor.description interface."
+        # user_tab_columns gives data default for columns
+        cursor.execute("""
+            SELECT column_name, data_default
+            FROM user_tab_cols
+            WHERE table_name = UPPER(%s)""", [table_name])
+        columns_default = {column: default if default != 'NULL' else None for column, default in cursor.fetchall()}
+
         self.cache_bust_counter += 1
         cursor.execute("SELECT * FROM {} WHERE ROWNUM < 2 AND {} > 0".format(
             self.connection.ops.quote_name(table_name),
@@ -67,8 +74,9 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         description = []
         for desc in cursor.description:
             name = force_text(desc[0])  # cx_Oracle always returns a 'str' on both Python 2 and 3
+            default = columns_default[name]
             name = name % {}  # cx_Oracle, for some reason, doubles percent signs.
-            description.append(FieldInfo(*(name.lower(),) + desc[1:]))
+            description.append(FieldInfo(*(name.lower(),) + desc[1:] + (default,)))
         return description
 
     def table_name_converter(self, name):

django/db/backends/postgresql/introspection.py

 from __future__ import unicode_literals
 
 import warnings
-from collections import namedtuple
 
 from django.db.backends.base.introspection import (
     BaseDatabaseIntrospection, FieldInfo, TableInfo,
@@ -9,8 +8,6 @@ from django.db.backends.base.introspection import (
 from django.utils.deprecation import RemovedInDjango21Warning
 from django.utils.encoding import force_text
 
-FieldInfo = namedtuple('FieldInfo', FieldInfo._fields + ('default',))
-
 
 class DatabaseIntrospection(BaseDatabaseIntrospection):
     # Maps type codes to Django Field types.

django/db/backends/sqlite3/introspection.py

 import re
 import warnings
-from collections import namedtuple
 
 from django.db.backends.base.introspection import (
     BaseDatabaseIntrospection, FieldInfo, TableInfo,
@@ -8,7 +7,6 @@ from django.db.backends.base.introspection import (
 from django.utils.deprecation import RemovedInDjango21Warning
 
 field_size_re = re.compile(r'^\s*(?:var)?char\s*\(\s*(\d+)\s*\)\s*$')
-FieldInfo = namedtuple('FieldInfo', FieldInfo._fields + ('default',))
 
 
 def get_field_size(name):