Bug 182895 Support sort on Level attribute.
Currently in OLAP engine we only support sort on level key value. We should go ahead to support sort on level attribute value.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/olap/data/impl/aggregation/sort/AggregationSortHelper.java
{
		this.base.close( );
		this.aggrValues.close( );
	}
	/*
	 * (non-Javadoc)
	 * @see org.eclipse.birt.data.engine.olap.data.util.IDiskArray#get(int)
	 */
	public Object get( int index ) throws IOException
	{
		this.index = index;
		return new CombinedAggrResultRow( (IAggregationResultRow) this.getCurrentBaseRow( ),
				(IAggregationResultRow) this.getCurrentKeyRow( ) );
	}
	/*
	 * (non-Javadoc)
	 * @see org.eclipse.birt.data.engine.olap.data.util.IDiskArray#size()
	 */
	public int size( )
	{
		return this.base.size( );
	}
}
/**
 * This class combine two AggregationResultRow object to one. Specifically, it will 
 * get level values from "base", and aggregation values from "key".
 * @author Administrator
 *
 */
class CombinedAggrResultRow implements IAggregationResultRow