code: @Override
  	public void open(InputSplit ignored) throws IOException {
  		try {
  			establishConnection();
  			statement = dbConn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
  			resultSet = statement.executeQuery(query);
  		} catch (SQLException se) {
  			close();
  			throw new IllegalArgumentException("open() failed." + se.getMessage(), se);
  		} catch (ClassNotFoundException cnfe) {
  			throw new IllegalArgumentException("JDBC-Class not found. - " + cnfe.getMessage(), cnfe);
  		}
  	}
docs: Connects to the source database and executes the query.
  
  @param ignored
  @throws IOException