transactions.cpp

This examples shows how the ScopedTransaction object operates in different situations.

#include <SimpleDB.h>

int main(int argc, char ** argv) {
  using namespace SimpleDB;
  try {

    Database db("simpledb-examples"); 

    {

      /*
       * This transaction is not committed, so the following query
       * will rollback.
       */
      ScopedTransaction trans(db);
      db.voidQuery("INSERT INTO sessions VALUES (5,'wont commit', datetime('now'))");
    }

    {

      /*
       * This transaction is not committed, so all changes
       * within it's scope will be rolled back, even though the
       * child transaction is committed.
       */
      ScopedTransaction trans(db);
      {
        ScopedTransaction trans(db);
        db.voidQuery("INSERT INTO sessions VALUES(5, 'try', datetime('now'))");
        trans.commit();
      }
    }

    /*
     * This query is not within the scope of any transaction,
     * so the database connection will be in autocommit mode and so
     * this query will be committed.
     */
    db.voidQuery("INSERT INTO sessions VALUES(5, 'autocommit', datetime('now'))");
    
    {
      /*
       * This transaction and it's child are committed, therefore these
       * queries will be committed
       */
      ScopedTransaction trans(db);
      {
        ScopedTransaction trans(db);
        std::cerr << "num: " << db.getTransactionCount() << std::endl;
        db.voidQuery("INSERT INTO sessions VALUES(5, 'commit', datetime('now'))");
        trans.commit();
      }
      std::cerr << "num: " << db.getTransactionCount() << std::endl;
      trans.commit();
    }

    std::cerr << "num: " << db.getTransactionCount() << std::endl;

    {

      ScopedTransaction trans(db);
      trans.rollback();
      
      /*
       * Throws an exception because the transaction is still in scope
       * but it is being rolled back
       */
      db.voidQuery("INSERT INTO sessions VALUES(5, 'try', datetime('now'))");

    }
  } catch (const std::exception& e) {
    std::cerr << "Exception: " << e.what() << std::endl;
  }
}