Bug 191644 Dataset don't be cached in Chart Builder.
Build ID: I20070517-1700 Birt Steps To Reproduce: 1. New a Chart. 2. Set dataset from remote db. 3. Switch tabs of Chart Builder, it is OK. 4. Shut off network. 5. Switch tabs of Chart Builder again. 6. Some exception will throw, it shows the db accessing is fail. Expected Result: The dataset should be cached. Actual Result: It looks like the dataset don't be cached. More information:
chart/org.eclipse.birt.chart.reportitem.ui/src/org/eclipse/birt/chart/reportitem/ui/ReportDataServiceProvider.java
}
	/**
	 * Generate computed columns for the given report item with the closest data
	 * set available.
	 * 
	 * @param handle
	 *            the handle of the report item. No aggregation created.
	 * 
	 * @return true if succeed,or fail if no column generated.
	 * @see DataUtil#generateComputedColumns(ReportItemHandle)
	 * 
	 */
	private List generateComputedColumns( ReportItemHandle handle )
			throws SemanticException
	{
		DataSetHandle dataSetHandle = handle.getDataSet( );
		if ( dataSetHandle == null )
		{
			dataSetHandle = DEUtil.getBindingHolder( handle ).getDataSet( );
		}
		if ( dataSetHandle != null )
		{
			List resultSetColumnList = DataUtil.getColumnList( dataSetHandle );
			ArrayList columnList = new ArrayList( );
			for ( Iterator iter = resultSetColumnList.iterator( ); iter.hasNext( ); )
			{
				ResultSetColumnHandle resultSetColumn = (ResultSetColumnHandle) iter.next( );
				ComputedColumn column = StructureFactory.newComputedColumn( handle,
						resultSetColumn.getColumnName( ) );
				column.setDataType( resultSetColumn.getDataType( ) );