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.tests/test/org/eclipse/birt/data/engine/binding/DataSetCacheTest.java
int appendLen = length - inputLen;
		char[] appendChar = new char[appendLen];
		for ( int i = 0; i < appendLen; i++ )
		{
			appendChar[i] = ' ';
		}
		String result = inputStr + new String( appendChar );
		return result;
	}
	/**
	 * Test the feature of clear cache
	 * @throws BirtException
	 */
	public void testClearCache( ) throws BirtException
	{
		this.dataSet.setCacheRowCount( 4 );
		DataEngineImpl myDataEngine = newDataEngine( );
		assertFalse( getDataSetCacheManager( myDataEngine ).doesLoadFromCache( ) );
		assertFalse( getDataSetCacheManager( myDataEngine ).doesSaveToCache( ) );
		QueryDefinition qd = newReportQuery( );
		rowBeArray = getRowExpr( );
		totalBeArray = getAggrExpr( );
		bindingNameRow = getRowExprName( );
		bindingExprRow = getAggrExprName( );
		prepareExprNameAndQuery( rowBeArray,
				bindingNameRow,
				totalBeArray,
				bindingExprRow,
				qd );
		IQueryResults qr = myDataEngine.prepare( qd, appContextMap )