Bug 168026 Still use the existing data binding even though the aggregate is different
I had a table in which a data binding which aggregates on a group. When I insert a new data item in the report, although the expressions are same, it aggregates on All, then it refered to the existing data binding. The expected behavior would be a new data binding is created with different aggregates.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ReportItemHandle.java
if ( column != null && !inForce )
		{
			return (ComputedColumnHandle) column.handle(
					getPropertyHandle( BOUND_DATA_COLUMNS_PROP ), columns
							.indexOf( column ) );
		}
		return (ComputedColumnHandle) getPropertyHandle(
				BOUND_DATA_COLUMNS_PROP ).addItem( addColumn );
	}
	/**
	 * Removes unused bound columns from the element. Bound columns of nested
	 * elements will not be removed. For example, if calls this method for a
	 * list thaat contains a text-data, unused bound columns on list are
	 * removed. While, unused columns on text-data still are kept.
	 * 
	 * @throws SemanticException
	 *             if bound column property is locked.
	 */
	public void removedUnusedColumnBindings( ) throws SemanticException
	{
		UnusedBoundColumnsMgr.removedUnusedBoundColumns( this );
	}
	/**
	 * Gets TOC handle.
	 * 
	 * @return toc handle
	 */
	public TOCHandle getTOC( )
	{
		PropertyHandle propHandle = getPropertyHandle( IReportItemModel.TOC_PROP );