Hi,
I think you need to use iv_first_time variable to avoid it if you are doing the code in do_prepare_output method.
If iv_first_time eq ABAP_TRUE.
lr_qs->add_selection_param( exporting iv_attr_name = 'CREATED_BY' iv_sign = 'I' iv_option = 'EQ' iv_low = LV_UNAME ).
Endif.
Thanks
Kumar