Bug 200471 Add "need not sort for grouping" option in report item
Currently when Data engine proceeds groups, it always sorts the result set according to given group key.However that should not be necessary when the raw data is already sorted. So we'd like to add new options so that user can indicate whether should we sort the data before grouping. In model, we should allow user to set a "need not do sort for grouping" option to all the report element that can be grouped(table, list,etc.)
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ListingHandle.java
* Represents slots and common properties in the two list-oriented elements:
 * table and list. A listing has on-start, on-row and on-finish script
 * properties as well as detail, footer, groups and header slots.
 * <p>
 * <ul>
 * <li>The on-start script called before the first row is retrieved from the
 * data set for this element. Called after the data set is open but before the
 * header band is created.
 * <li>The on-row script called for each row retrieved from the data set for
 * this element, but before creating any content for that row.
 * <li>The on-finish script called after the last row is read from the data set
 * for this element, but before the footer band is created.
 * </ul>
 * 
 * @see org.eclipse.birt.report.model.elements.ListingElement
 * @see SlotHandle
 */
public abstract class ListingHandle extends ReportItemHandle
		implements
			IListingElementModel
{
	/**
	 * Constructs a listing handle with the given design and the element. The
	 * application generally does not create handles directly. Instead, it uses
	 * one of the navigation methods available on other element handles.
	 * 
	 * @param module
	 *            the module
	 * @param element
	 *            the model representation of the element