Added AutoField introspection for MySQL

Refs #23748.

django/db/backends/mysql/base.py

@@ -173,6 +173,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_binary_field = six.PY2
     supports_regex_backreferencing = False
     supports_date_lookup_using_string = False
+    can_introspect_autofield = True
     can_introspect_binary_field = False
     can_introspect_small_integer_field = True
     supports_timezones = False

django/db/backends/mysql/introspection.py

+from collections import namedtuple
 import re
 from .base import FIELD_TYPE
 from django.utils.datastructures import OrderedSet
 from django.db.backends import BaseDatabaseIntrospection, FieldInfo, TableInfo
 from django.utils.encoding import force_text
 
+FieldInfo = namedtuple('FieldInfo', FieldInfo._fields + ('extra',))
 
 foreign_key_re = re.compile(r"\sCONSTRAINT `[^`]*` FOREIGN KEY \(`([^`]*)`\) REFERENCES `([^`]*)` \(`([^`]*)`\)")
 
@@ -32,6 +34,12 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         FIELD_TYPE.VAR_STRING: 'CharField',
     }
 
+    def get_field_type(self, data_type, description):
+        field_type = super(DatabaseIntrospection, self).get_field_type(data_type, description)
+        if field_type == 'IntegerField' and 'auto_increment' in description.extra:
+            return 'AutoField'
+        return field_type
+
     def get_table_list(self, cursor):
         """
         Returns a list of table and view names in the current database.
@@ -44,28 +52,33 @@ class DatabaseIntrospection(BaseDatabaseIntrospection):
         """
         Returns a description of the table, with the DB-API cursor.description interface."
         """
-        # varchar length returned by cursor.description is an internal length,
-        # not visible length (#5725), use information_schema database to fix this
-        cursor.execute("""
-            SELECT column_name, character_maximum_length FROM information_schema.columns
-            WHERE table_name = %s AND table_schema = DATABASE()
-                AND character_maximum_length IS NOT NULL""", [table_name])
-        length_map = dict(cursor.fetchall())
-
-        # Also getting precision and scale from information_schema (see #5014)
+        # information_schema database gives more accurate results for some figures:
+        # - varchar length returned by cursor.description is an internal length,
+        #   not visible length (#5725)
+        # - precision and scale (for decimal fields) (#5014)
+        # - auto_increment is not available in cursor.description
+        InfoLine = namedtuple('InfoLine', 'col_name data_type max_len num_prec num_scale extra')
         cursor.execute("""
-            SELECT column_name, numeric_precision, numeric_scale FROM information_schema.columns
-            WHERE table_name = %s AND table_schema = DATABASE()
-                AND data_type='decimal'""", [table_name])
-        numeric_map = dict((line[0], tuple(int(n) for n in line[1:])) for line in cursor.fetchall())
+            SELECT column_name, data_type, character_maximum_length, numeric_precision, numeric_scale, extra
+            FROM information_schema.columns
+            WHERE table_name = %s AND table_schema = DATABASE()""", [table_name])
+        field_info = dict((line[0], InfoLine(*line)) for line in cursor.fetchall())
 
         cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
-        return [FieldInfo(*((force_text(line[0]),)
+        to_int = lambda i: int(i) if i is not None else i
+        fields = []
+        for line in cursor.description:
+            col_name = force_text(line[0])
+            fields.append(
+                FieldInfo(*((col_name,)
                             + line[1:3]
-                            + (length_map.get(line[0], line[3]),)
-                            + numeric_map.get(line[0], line[4:6])
-                            + (line[6],)))
-            for line in cursor.description]
+                            + (to_int(field_info[col_name].max_len) or line[3],
+                               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,)))
+            )
+        return fields
 
     def _name_to_index(self, cursor, table_name):
         """