取消与设置CDS本地排序

   取消CDS本地排序.
cds.IndexDefs.Update;
    if cds.IndexName<>'' then
    begin
      if cds.IndexDefs.IndexOf('index1')>=0 then cds.DeleteIndex('index1');
      cds.IndexDefs.Clear;
      cds.IndexName:='';
    end;
设置CDS本地排序
  cds.IndexDefs.Update;
    cds..AddIndex('index1','sum_num',[ixDescending]);
    cds.IndexName:='index2';
    cds.First;