[Cppcms-users] Bug about transaction in cppdb

[陈抒 <csf...@gm...>]

Hello,Artyom:

  I run into one problem,I try to update one record in one MySQL table
using transaction like so:

  static shared_ptr<prize> award(shared_ptr<prize> p,shared_ptr<user> user,
int promo_id){
    my_application & app = app_singleton_holder::Instance();
    cppdb::session session(app.config().master_mysql_uri);
    cppdb::statement stat;

    cppdb::transaction guard(session);
    cppdb::result res = session <<"select account_id from event_prize where
prizeId = ? and account_id is NULL"<< p->id();
    unsigned int account_id;
    if(res.next() ){
 stat = session << "update event_prize set account_id=? ,award_time=now()
where prizeId=?"
   << user->account_id() << p->id();
 stat.exec();
guard.commit();
 //发送站内短信
send_message(p , user , promo_id);
BOOSTER_NOTICE("award") << "obtain a real prize, the account_id is:" <<
user->account_id() << ".the prize_id is:" << p->id();
 return p;
    }else{
guard.rollback();
 BOOSTER_NOTICE("award") << "already have got a prize, the account_id
is:"<< user->account_id() << ".the prize_id is:" << p->id();
 return create_default_prize(user,promo_id);
    }
  }

  Then I write a Java test application using TestNG to test my service with
50 threads.But the service updates one record twice.Here is my log:

20071:2011-10-30 11:48:37 GMT; award, notice: obtain a real prize, the
account_id is:2011.the prize_id is:906326 (default_prize_policy.h:196)
20074:2011-10-30 11:48:37 GMT; award, notice: already have got a prize, the
account_id is:2011.the prize_id is:906326 (default_prize_policy.h:200)
20121:2011-10-30 11:48:37 GMT; award, notice: obtain a real prize, the
account_id is:2011.the prize_id is:906326 (default_prize_policy.h:196)

  Maybe it's a bug.Another question,How to change the transaction isolation
level for MySQL?


陈抒
Best regards
http://blog.csdn.net/sheismylife