storage: code refactoring for backends to connect to the database

neo/storage/database/importer.py

@@ -308,6 +308,9 @@ class ImporterDatabaseManager(DatabaseManager):
                  """.split():
             setattr(self, x, getattr(self.db, x))
 
+    def _connect(self):
+        pass
+
     def commit(self):
         self.db.commit()
         self._last_commit = time.time()

neo/storage/database/manager.py

@@ -52,6 +52,8 @@ class DatabaseManager(object):
 
     ENGINES = ()
 
+    _deferred = 0
+
     def __init__(self, database, engine=None, wait=0):
         """
             Initialize the object.
@@ -62,8 +64,8 @@ class DatabaseManager(object):
                                  % (engine, self.ENGINES))
             self._engine = engine
         self._wait = wait
-        self._deferred = 0
         self._parse(database)
+        self._connect()
 
     def __getattr__(self, attr):
         if attr == "_getPartition":
@@ -78,6 +80,10 @@ class DatabaseManager(object):
     def _parse(self, database):
         """Called during instantiation, to process database parameter."""
 
+    @abstract
+    def _connect(self):
+        """Connect to the database"""
+
     def setup(self, reset=0):
         """Set up a database, discarding existing data first if reset is True
         """

neo/storage/database/mysqldb.py

@@ -56,12 +56,6 @@ class MySQLDatabaseManager(DatabaseManager):
 
     _max_allowed_packet = 32769 * 1024
 
-    def __init__(self, *args, **kw):
-        super(MySQLDatabaseManager, self).__init__(*args, **kw)
-        self.conn = None
-        self._config = {}
-        self._connect()
-
     def _parse(self, database):
         """ Get the database credentials (username, password, database) """
         # expected pattern : [user[:password]@]database[(~|.|/)unix_socket]
@@ -93,6 +87,7 @@ class MySQLDatabaseManager(DatabaseManager):
                 logging.exception('Connection to MySQL failed, retrying.')
                 time.sleep(1)
         self._active = 0
+        self._config = {}
         conn = self.conn
         conn.autocommit(False)
         conn.query("SET SESSION group_concat_max_len = %u" % (2**32-1))

neo/storage/database/sqlite.py

@@ -69,11 +69,6 @@ class SQLiteDatabaseManager(DatabaseManager):
 
     VERSION = 1
 
-    def __init__(self, *args, **kw):
-        super(SQLiteDatabaseManager, self).__init__(*args, **kw)
-        self._config = {}
-        self._connect()
-
     def _parse(self, database):
         self.db = os.path.expanduser(database)
 
@@ -83,6 +78,7 @@ class SQLiteDatabaseManager(DatabaseManager):
     def _connect(self):
         logging.info('connecting to SQLite database %r', self.db)
         self.conn = sqlite3.connect(self.db, check_same_thread=False)
+        self._config = {}
 
     def _commit(self):
         retry_if_locked(self.conn.commit)