@Override
	public DatabaseSource getNewDatabaseSource() {
		try{
			if(prefetchConnectionURL != null){
				Connection preConn = DriverManager.getConnection(prefetchConnectionURL);
				logger.info("start db prefetch...");
				startPrefetch(preConn);
				logger.info("prefetch ok~");
			}
			Connection writeConn = DriverManager.getConnection(writeConnectionURL);
			logger.info("new connection~");
			SimpleDatabaseSource dbs = new SimpleDatabaseSource(writeConn);
			dbs.scanPlanList = this.scanPlanList;
			return dbs;
			
		} catch (SQLException ex) {
            logger.log(Level.SEVERE, "create database connection", ex);
        }
		return null;
	}