Return namedtuple from get_table_description

We don't make use of it currently to not break third-party db
backends.

django/db/backends/__init__.py

@@ -4,6 +4,7 @@ try:
     from django.utils.six.moves import _thread as thread
 except ImportError:
     from django.utils.six.moves import _dummy_thread as thread
+from collections import namedtuple
 from contextlib import contextmanager
 
 from django.conf import settings
@@ -918,6 +919,12 @@ class BaseDatabaseOperations(object):
         """
         return params
 
+
+# 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'
+)
+
 class BaseDatabaseIntrospection(object):
     """
     This class encapsulates all backend-specific introspection utilities

django/db/backends/mysql/introspection.py

 import re
 from .base import FIELD_TYPE
 
-from django.db.backends import BaseDatabaseIntrospection
+from django.db.backends import BaseDatabaseIntrospection, FieldInfo
 
 
 foreign_key_re = re.compile(r"\sCONSTRAINT `[^`]*` FOREIGN KEY \(`([^`]*)`\) REFERENCES `([^`]*)` \(`([^`]*)`\)")
@@ -47,7 +47,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         length_map = dict(cursor.fetchall())
 
         cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
-        return [line[:3] + (length_map.get(line[0], line[3]),) + line[4:]
+        return [FieldInfo(*(line[:3] + (length_map.get(line[0], line[3]),) + line[4:]))
             for line in cursor.description]
 
     def _name_to_index(self, cursor, table_name):

django/db/backends/oracle/introspection.py

-from django.db.backends import BaseDatabaseIntrospection
+from django.db.backends import BaseDatabaseIntrospection, FieldInfo
 import cx_Oracle
 import re
 
@@ -47,7 +47,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         cursor.execute("SELECT * FROM %s WHERE ROWNUM < 2" % self.connection.ops.quote_name(table_name))
         description = []
         for desc in cursor.description:
-            description.append((desc[0].lower(),) + desc[1:])
+            description.append(FieldInfo(*((desc[0].lower(),) + desc[1:])))
         return description
 
     def table_name_converter(self, name):

django/db/backends/postgresql_psycopg2/introspection.py

 from __future__ import unicode_literals
 
-from django.db.backends import BaseDatabaseIntrospection
+from django.db.backends import BaseDatabaseIntrospection, FieldInfo
 
 
 class DatabaseIntrospection(BaseDatabaseIntrospection):
@@ -45,7 +45,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
             WHERE table_name = %s""", [table_name])
         null_map = dict(cursor.fetchall())
         cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
-        return [line[:6] + (null_map[line[0]]=='YES',)
+        return [FieldInfo(*(line[:6] + (null_map[line[0]]=='YES',)))
                 for line in cursor.description]
 
     def get_relations(self, cursor, table_name):

django/db/backends/sqlite3/introspection.py

 import re
-from django.db.backends import BaseDatabaseIntrospection
+from django.db.backends import BaseDatabaseIntrospection, FieldInfo
 
 field_size_re = re.compile(r'^\s*(?:var)?char\s*\(\s*(\d+)\s*\)\s*$')
 
@@ -60,7 +60,7 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
 
     def get_table_description(self, cursor, table_name):
         "Returns a description of the table, with the DB-API cursor.description interface."
-        return [(info['name'], info['type'], None, info['size'], None, None,
+        return [FieldInfo(info['name'], info['type'], None, info['size'], None, None,
                  info['null_ok']) for info in self._table_info(cursor, table_name)]
 
     def get_relations(self, cursor, table_name):