run method
Runs the SQL of the schema with session, and throws if it fails: in a
transaction of its own, if session is a Connection or another that
runs them, or in that of a transaction it is of.
Implementation
Future<int> run(Session session) async {
if (session is SessionExecutor) {
return (session as SessionExecutor).runTx(_execute);
}
return _execute(session);
}