storage: update backend version between each migration step

neo/storage/database/manager.py

@@ -161,11 +161,14 @@ class DatabaseManager(object):
                 "The database can not be upgraded because you have unfinished"
                 " transactions. Use an older version of NEO to verify them.")
 
-    def _getVersion(self):
+    def migrate(self):
         version = int(self.getConfiguration("version") or 0)
         if self.VERSION < version:
             raise DatabaseFailure("The database can not be downgraded.")
-        return version
+        while version < self.VERSION:
+            version += 1
+            getattr(self, '_migrate%s' % version)()
+            self.setConfiguration("version", version)
 
     def doOperation(self, app):
         pass

neo/storage/database/mysqldb.py

@@ -176,6 +176,10 @@ class MySQLDatabaseManager(DatabaseManager):
             if e.args[0] != NO_SUCH_TABLE:
                 raise
 
+    def _migrate1(self):
+        self._checkNoUnfinishedTransactions()
+        self.query("DROP TABLE IF EXISTS ttrans")
+
     def _setup(self, dedup=False):
         self._config.clear()
         q = self.query
@@ -188,14 +192,9 @@ class MySQLDatabaseManager(DatabaseManager):
                      name VARBINARY(255) NOT NULL PRIMARY KEY,
                      value VARBINARY(255) NULL
                  ) ENGINE=""" + engine)
-        else:
-            # Automatic migration.
-            version = self._getVersion()
-            if version < 1:
-                self._checkNoUnfinishedTransactions()
-                q("DROP TABLE IF EXISTS ttrans")
-
             self._setConfiguration("version", self.VERSION)
+        else:
+            self.migrate()
 
         # The table "pt" stores a partition table.
         q("""CREATE TABLE IF NOT EXISTS pt (

neo/storage/database/sqlite.py

@@ -112,6 +112,10 @@ class SQLiteDatabaseManager(DatabaseManager):
             if not e.args[0].startswith("no such table:"):
                 raise
 
+    def _migrate1(self):
+        self._checkNoUnfinishedTransactions()
+        self.query("DROP TABLE IF EXISTS ttrans")
+
     def _setup(self, dedup=False):
         # SQLite does support transactional Data Definition Language statements
         # but unfortunately, the built-in Python binding automatically commits
@@ -126,14 +130,9 @@ class SQLiteDatabaseManager(DatabaseManager):
             q("CREATE TABLE IF NOT EXISTS config ("
               "  name TEXT NOT NULL PRIMARY KEY,"
               "  value TEXT)")
-        else:
-            # Automatic migration.
-            version = self._getVersion()
-            if version < 1:
-                self._checkNoUnfinishedTransactions()
-                q("DROP TABLE IF EXISTS ttrans")
-
             self._setConfiguration("version", self.VERSION)
+        else:
+            self.migrate()
 
         # The table "pt" stores a partition table.
         q("""CREATE TABLE IF NOT EXISTS pt (