Bug 136740 Error exporting data from a grouped report.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManagerUtil.java
*/
	private static void testGroupNameValidation( ExprManager exprManager ) throws DataException
	{
		HashMap map = exprManager.getGroupKeys( );
		Iterator it = map.keySet( ).iterator( );
		while ( it.hasNext( ) )
		{
			Integer level = (Integer)it.next( );
			exprManager.setEntryGroupLevel( level.intValue( ) );
			
			if(!ExpressionCompilerUtil.hasColumnRow( map.get( level ).toString( ), exprManager ))
			{
				exprManager.setEntryGroupLevel( ExprManager.OVERALL_GROUP );
				throw new DataException( ResourceConstants.INVALID_GROUP_KEY, new Object[]{ map.get( level ).toString( ), level});
			}
		}
		exprManager.setEntryGroupLevel( ExprManager.OVERALL_GROUP );
	}
	
	/**
	 * Test whether there are dependency cycles in exprManager.
	 * 
	 * @param exprManager
	 * @return
	 * @throws DataException
	 */
	private static void testDependencyCycle( ExprManager exprManager ) throws DataException
	{
		List result = new ArrayList( );
		Iterator it = exprManager.getColumnNames( ).iterator( );