Bug 145478 Unable "Select Value" in the Join data set's filter
Step to reproduce: 1.new a join data set(please use the attached file) 2.right click the dataset and click the Edit 3.go to the Filter pane and set a filer 4.click the list of Value1 Actual result: A warning pop up and cant select Value.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/data/ui/util/DataSetProvider.java
HashSet orgColumnNameSet = new HashSet( );
		
		HashSet uniqueColumnNameSet = new HashSet( );
		for ( int n = 0; n < columns.length; n++ )
		{
			orgColumnNameSet.add( metaData.getColumnName( n + 1 ) );
		}
		for ( int n = 0; n < columns.length; n++ )
		{
			columns[n] = new DataSetViewData( );
			columns[n].setParent( dataSet );
			columns[n].setDataType( metaData.getColumnType( n + 1 ) );
			columns[n].setDataTypeName( metaData.getColumnTypeName( n + 1 ) );
			columns[n].setPosition( n + 1 );
			columns[n].setAlias( metaData.getColumnAlias( n + 1 ) );
			columns[n].setComputedColumn( metaData.isComputedColumn( n + 1 ) );
			String columnName = metaData.getColumnName( n + 1 );
			
			String uniqueColumnName = getUniqueName( orgColumnNameSet,
					uniqueColumnNameSet,
					columnName,
					n );
			
			columns[n].setDataSetColumnName( uniqueColumnName );
			uniqueColumnNameSet.add( uniqueColumnName );
			
			if ( !uniqueColumnName.equals( columnName ) )