Bug 206861 The data set cache should handle IOException and the cancel request from customer
The data set data will be saved into disk file in the first query and it will be loaded in the later time. The processing of write disk file may be cancelled by customer request or IOException. Using the data from the bad file will cause error.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/executor/cache/disk/DiskDataExport.java
/**
	 * get a ObjectFileWithCache object for goal file 
	 * @return
	 */
	public abstract IRowIterator getRowIterator();
	
	/**
	 * 
	 * @return
	 */
	public abstract void close();
	
	/**
	 * A util method for sub class
	 * @param resultObjects
	 * @param stopSign
	 * @return
	 * @throws IOException
	 */
	protected int innerExportStartData( IResultObject[] resultObjects, StopSign stopSign )
			throws IOException
	{
		outputResultObjects( resultObjects, 0, stopSign );
		return resultObjects.length;
	}
	 
	/**
	 * A util method for sub class
	 *