Bug 152430 Key can modify to empty string
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ResultSetColumnHandle.java
/**
	 * Sets the position that this column is in the result set.
	 * 
	 * @param position
	 *            the position to set
	 */
	public void setPosition( Integer position )
	{
		setPropertySilently( ResultSetColumn.POSITION_MEMBER, position );
	}
	/**
	 * Returns the native data type.
	 * 
	 * @return the result set column native data type.
	 */
	public Integer getNativeDataType( )
	{
		return (Integer) getProperty( ResultSetColumn.NATIVE_DATA_TYPE_MEMBER );
	}
	/**
	 * Sets the result set column native data type.
	 * 
	 * @param dataType
	 *            the native data type to set.
	 */
	public void setNativeDataType( Integer dataType )
	{
		setPropertySilently( ResultSetColumn.NATIVE_DATA_TYPE_MEMBER, dataType );
	}
}