If the fact table is called "Orders", it is likely that has a order_id or order_number field which value is incremental. In that case, I recomend you to use it to limit the load for the fields on the next load, something like this:
// the first time you run this, you will have to manually define the value of the variable to avoid errors
// set vMaxOrderN =0;
Orders:
LOAD order_id,
item_descr,
item_descr
//include other fields here
FROM source_file.csv (txt)
where order_id > '$(vMaxOrderN)';
let vMaxOrderN = max('order_id');
// Whenever you want to make a full reload, just reset vMaxOrderN =0
