Improved implementation of PreparedStatement.getMetaData(). The previous implementation created a new ResultSetMetaData object each time this method is called which is quite costly if it is called from inside a fetch-loop. As the ResultSetMetaData is static for a PreparedStatement it is better to create it once, cache it in the PreparedStatement object and return the cached object for next calls to PreparedStatement.getMetaData(). Also it reuses now all the methods of ResultSetMetaData class, which implies less code and easier future maintenance. The private method getColumnIdx(int column) also is no longer needed and has been removed.