qa: speed up SQlite tests by accessing DBs in unsafe mode (e.g. no sync)

neo/scripts/runner.py

@@ -402,6 +402,8 @@ Environment Variables:
         return runner.buildReport(self.add_status)
 
 def main(args=None):
+    from neo.storage.database.manager import DatabaseManager
+    DatabaseManager.UNSAFE = True
     runner = TestRunner()
     runner.run()
     return sys.exit(not runner.was_successful())

neo/storage/database/manager.py

@@ -53,6 +53,7 @@ class DatabaseManager(object):
     """This class only describes an interface for database managers."""
 
     ENGINES = ()
+    UNSAFE = False
 
     _deferred = 0
     _duplicating = _repairing = None

neo/storage/database/sqlite.py

@@ -78,6 +78,10 @@ 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)
+        if self.UNSAFE:
+            q = self.query
+            q("PRAGMA synchronous = OFF")
+            q("PRAGMA journal_mode = MEMORY")
         self._config = {}
 
     def _commit(self):
@@ -108,6 +112,10 @@ class SQLiteDatabaseManager(DatabaseManager):
                 raise
 
     def _setup(self):
+        # SQLite does support transactional Data Definition Language statements
+        # but unfortunately, the built-in Python binding automatically commits
+        # between such statements. This anti-feature causes this method to be
+        # relatively slow; unit tests enables the UNSAFE boolean flag.
         self._config.clear()
         q = self.query