beginTransaction

Start a database transaction creating a Transaction instance.

For an overview see page McoSqlEngine

Prototypes

 
    Transaction* SqlEngine::beginTransaction(Transaction::Mode mode, 
                            int priority = 0, 
                            Transaction::IsolationLevel level = 
                            Transaction::DefaultIsolationLevel)
 

Arguments

mode	A Transaction::Mode: Exclusive, ReadOnly, ReadWrite or Update
priority	An integer value specifying the transaction priority. (See page Transaction Priorities and Scheduling for further details)
level	A Transaction::IsolationLevel: DefaultIsolationLevel, ReadCommitted, RepeatableRead or Serializable. (See page Transaction Isolation Levels for further details)

Description

This method starts a database transaction creating a Transaction instance. When completed, the Transaction method commit() or rollback() must be called to close the transaction, and release() to release system resources associated with the transaction. In multi-threaded applications, if it is necessary to share a single database connection between multiple threads, the McoSqlSession class must be used and it's Database member's beginTransaction() method

Returns

This method returns a Transaction or throws a RuntimeException in the case of an error.

Example

     
    const char * dbname = "SqlDb";
     
    int main(int argc, char* argv[])
    {
        McoSqlEngine engine;
        ...
        engine.open(db_name,  // database name
                SqlDb_get_dictionary(),  // database dictionary
                DATABASE_SIZE,  // database size
                MEMORY_PAGE_SIZE,  // page size
                MAP_ADDRESS); // mapping address for shared memory mode
        ...
        Transaction* trans = engine.beginTransaction(Transaction::ReadWrite);
            
        engine.executeStatement(trans, "update Member set balance=%i where id=%i",
            
                        fromBalance, idFrom);
            
        engine.executeStatement(trans, "update Member set balance=%i where id=%i",
            
                        toBalance, idTo);
            
        trans->commit();
            
        trans->release();
            
        ...
    }