Factored out common code in database backends.

django/db/backends/__init__.py

@@ -11,6 +11,7 @@ from contextlib import contextmanager
 
 from django.conf import settings
 from django.db import DEFAULT_DB_ALIAS
+from django.db.backends.signals import connection_created
 from django.db.backends import util
 from django.db.transaction import TransactionManagementError
 from django.utils.functional import cached_property
@@ -52,6 +53,17 @@ class BaseDatabaseWrapper(object):
 
     __hash__ = object.__hash__
 
+    def _valid_connection(self):
+        return self.connection is not None
+
+    def _cursor(self):
+        if not self._valid_connection():
+            conn_params = self.get_connection_params()
+            self.connection = self.get_new_connection(conn_params)
+            self.init_connection_state()
+            connection_created.send(sender=self.__class__, connection=self)
+        return self.create_cursor()
+
     def _commit(self):
         if self.connection is not None:
             return self.connection.commit()

django/db/backends/mysql/base.py

@@ -33,19 +33,16 @@ from MySQLdb.constants import FIELD_TYPE, CLIENT
 from django.conf import settings
 from django.db import utils
 from django.db.backends import *
-from django.db.backends.signals import connection_created
 from django.db.backends.mysql.client import DatabaseClient
 from django.db.backends.mysql.creation import DatabaseCreation
 from django.db.backends.mysql.introspection import DatabaseIntrospection
 from django.db.backends.mysql.validation import DatabaseValidation
 from django.utils.encoding import force_str
-from django.utils.functional import cached_property
 from django.utils.safestring import SafeBytes, SafeText
 from django.utils import six
 from django.utils import timezone
 
 # Raise exceptions for database warnings if DEBUG is on
-from django.conf import settings
 if settings.DEBUG:
     warnings.filterwarnings("error", category=Database.Warning)
 
@@ -454,12 +451,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         cursor.execute('SET SQL_AUTO_IS_NULL = 0')
         cursor.close()
 
-    def _cursor(self):
-        if not self._valid_connection():
-            conn_params = self.get_connection_params()
-            self.connection = self.get_new_connection(conn_params)
-            self.init_connection_state()
-            connection_created.send(sender=self.__class__, connection=self)
+    def create_cursor(self):
         cursor = self.connection.cursor()
         return CursorWrapper(cursor)
 

django/db/backends/oracle/base.py

@@ -48,7 +48,6 @@ except ImportError as e:
 from django.conf import settings
 from django.db import utils
 from django.db.backends import *
-from django.db.backends.signals import connection_created
 from django.db.backends.oracle.client import DatabaseClient
 from django.db.backends.oracle.creation import DatabaseCreation
 from django.db.backends.oracle.introspection import DatabaseIntrospection
@@ -521,9 +520,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         self.cursor().execute('SET CONSTRAINTS ALL IMMEDIATE')
         self.cursor().execute('SET CONSTRAINTS ALL DEFERRED')
 
-    def _valid_connection(self):
-        return self.connection is not None
-
     def _connect_string(self):
         settings_dict = self.settings_dict
         if not settings_dict['HOST'].strip():
@@ -537,8 +533,8 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         return "%s/%s@%s" % (settings_dict['USER'],
                              settings_dict['PASSWORD'], dsn)
 
-    def create_cursor(self, conn):
-        return FormatStylePlaceholderCursor(conn)
+    def create_cursor(self):
+        return FormatStylePlaceholderCursor(self.connection)
 
     def get_connection_params(self):
         conn_params = self.settings_dict['OPTIONS'].copy()
@@ -551,7 +547,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         return Database.connect(conn_string, **conn_params)
 
     def init_connection_state(self):
-        cursor = self.create_cursor(self.connection)
+        cursor = self.create_cursor()
         # Set the territory first. The territory overrides NLS_DATE_FORMAT
         # and NLS_TIMESTAMP_FORMAT to the territory default. When all of
         # these are set in single statement it isn't clear what is supposed
@@ -572,7 +568,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
             # This check is performed only once per DatabaseWrapper
             # instance per thread, since subsequent connections will use
             # the same settings.
-            cursor = self.create_cursor(self.connection)
+            cursor = self.create_cursor()
             try:
                 cursor.execute("SELECT 1 FROM DUAL WHERE DUMMY %s"
                                % self._standard_operators['contains'],
@@ -602,14 +598,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
             # stmtcachesize is available only in 4.3.2 and up.
             pass
 
-    def _cursor(self):
-        if not self._valid_connection():
-            conn_params = self.get_connection_params()
-            self.connection = self.get_new_connection(conn_params)
-            self.init_connection_state()
-            connection_created.send(sender=self.__class__, connection=self)
-        return self.create_cursor(self.connection)
-
     # Oracle doesn't support savepoint commits.  Ignore them.
     def _savepoint_commit(self, sid):
         pass

django/db/backends/postgresql_psycopg2/base.py

@@ -8,7 +8,6 @@ import sys
 
 from django.db import utils
 from django.db.backends import *
-from django.db.backends.signals import connection_created
 from django.db.backends.postgresql_psycopg2.operations import DatabaseOperations
 from django.db.backends.postgresql_psycopg2.client import DatabaseClient
 from django.db.backends.postgresql_psycopg2.creation import DatabaseCreation
@@ -205,12 +204,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         self.connection.set_isolation_level(self.isolation_level)
         self._get_pg_version()
 
-    def _cursor(self):
-        if self.connection is None:
-            conn_params = self.get_connection_params()
-            self.connection = self.get_new_connection(conn_params)
-            self.init_connection_state()
-            connection_created.send(sender=self.__class__, connection=self)
+    def create_cursor(self):
         cursor = self.connection.cursor()
         cursor.tzinfo_factory = utc_tzinfo_factory if settings.USE_TZ else None
         return CursorWrapper(cursor)

django/db/backends/sqlite3/base.py

@@ -14,7 +14,6 @@ import sys
 
 from django.db import utils
 from django.db.backends import *
-from django.db.backends.signals import connection_created
 from django.db.backends.sqlite3.client import DatabaseClient
 from django.db.backends.sqlite3.creation import DatabaseCreation
 from django.db.backends.sqlite3.introspection import DatabaseIntrospection
@@ -344,13 +343,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
     def init_connection_state(self):
         pass
 
-    def _cursor(self):
-        if self.connection is None:
-            conn_params = self.get_connection_params()
-            self.connection = self.get_new_connection(conn_params)
-            self.init_connection_state()
-            connection_created.send(sender=self.__class__, connection=self)
-
+    def create_cursor(self):
         return self.connection.cursor(factory=SQLiteCursorWrapper)
 
     def check_constraints(self, table_names=None):