Bug 213907 Provide a copy constructor for SubqueryDefinition.
Engine need a copy constructor to generate a SubqueryDefinition from an ISubqueryDefinition and change the name of the query.
data/org.eclipse.birt.report.data.adapter/src/org/eclipse/birt/report/data/adapter/impl/DataRequestSessionImpl.java
* @param dataSetHandles
	 * @throws BirtException
	 */
	private void clearCache( Set dataSetHandles )
	{
		Iterator it = dataSetHandles.iterator( );
		while ( it.hasNext( ) )
		{
			try
			{
				DataSetHandle dsHandle = (DataSetHandle) it.next( );
				BaseDataSourceDesign baseDataSource = this.modelAdaptor.adaptDataSource( dsHandle.getDataSource( ) );
				BaseDataSetDesign baseDataSet = this.modelAdaptor.adaptDataSet( dsHandle );
				this.dataEngine.clearCache( baseDataSource, baseDataSet );
				if ( dsHandle instanceof JointDataSetHandle )
				{
					Set parentSet = new HashSet( );
					Iterator parentIt = ( (JointDataSetHandle) dsHandle ).dataSetsIterator( );
					while ( parentIt != null && parentIt.hasNext( ) )
					{
						parentSet.add( parentIt.next( ) );
					}
					clearCache( parentSet );
				}
			}
			catch ( Exception e )
			{
				
			}
		}