Factorized schema_editor() at BaseDatabaseWrapper level

5 files changed, 12 insertions, 17 deletions

diff --git a/django/db/backends/__init__.py b/django/db/backends/__init__.py
index 1f0e7b255c..9873d9cba6 100644
--- a/django/db/backends/__init__.py
+++ b/django/db/backends/__init__.py
@@ -37,6 +37,7 @@ class BaseDatabaseWrapper(object):
     """
     ops = None
     vendor = 'unknown'
+    SchemaEditorClass = None
 
     queries_limit = 9000
 
@@ -479,8 +480,13 @@ class BaseDatabaseWrapper(object):
         )
 
     def schema_editor(self, *args, **kwargs):
-        "Returns a new instance of this backend's SchemaEditor"
-        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a schema_editor() method')
+        """
+        Returns a new instance of this backend's SchemaEditor.
+        """
+        if self.SchemaEditorClass is None:
+            raise NotImplementedError(
+                'The SchemaEditorClass attribute of this database wrapper is still None')
+        return self.SchemaEditorClass(self, *args, **kwargs)
 
 
 class BaseDatabaseFeatures(object):
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index aefe4262e6..7223780081 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -434,6 +434,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     }
 
     Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
 
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
@@ -557,10 +558,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
                         table_name, column_name, bad_row[1],
                         referenced_table_name, referenced_column_name))
 
-    def schema_editor(self, *args, **kwargs):
-        "Returns a new instance of this backend's SchemaEditor"
-        return DatabaseSchemaEditor(self, *args, **kwargs)
-
     def is_usable(self):
         try:
             self.connection.ping()
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index e48c82f0d8..083ba18daa 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -593,6 +593,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     })
 
     Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
 
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
@@ -693,10 +694,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
                     six.reraise(utils.IntegrityError, utils.IntegrityError(*tuple(e.args)), sys.exc_info()[2])
                 raise
 
-    def schema_editor(self, *args, **kwargs):
-        "Returns a new instance of this backend's SchemaEditor"
-        return DatabaseSchemaEditor(self, *args, **kwargs)
-
     # Oracle doesn't support releasing savepoints. But we fake them when query
     # logging is enabled to keep query counts consistent with other backends.
     def _savepoint_commit(self, sid):
diff --git a/django/db/backends/postgresql_psycopg2/base.py b/django/db/backends/postgresql_psycopg2/base.py
index 975eee4df2..7de52d7592 100644
--- a/django/db/backends/postgresql_psycopg2/base.py
+++ b/django/db/backends/postgresql_psycopg2/base.py
@@ -91,6 +91,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     }
 
     Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
 
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
@@ -198,10 +199,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         else:
             return True
 
-    def schema_editor(self, *args, **kwargs):
-        "Returns a new instance of this backend's SchemaEditor"
-        return DatabaseSchemaEditor(self, *args, **kwargs)
-
     @cached_property
     def psycopg2_version(self):
         version = psycopg2.__version__.split(' ', 1)[0]
diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index 0e1070e6e5..349fae0253 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -351,6 +351,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     }
 
     Database = Database
+    SchemaEditorClass = DatabaseSchemaEditor
 
     def __init__(self, *args, **kwargs):
         super(DatabaseWrapper, self).__init__(*args, **kwargs)
@@ -489,9 +490,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         """
         self.cursor().execute("BEGIN")
 
-    def schema_editor(self, *args, **kwargs):
-        "Returns a new instance of this backend's SchemaEditor"
-        return DatabaseSchemaEditor(self, *args, **kwargs)
 
 FORMAT_QMARK_REGEX = re.compile(r'(?<!%)%s')