@Gopal B​ Hi. I see that there is a row number and a select on another table to populate a column. Did you execute that part alone and see how much time that takes on your 10% data?

Also I see that you are using row_number function to just generate a incremental id, is it possible you can achieve the same with GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( [ START WITH start ] [ INCREMENT BY step ] ) ] ] ? These might avoid a full table scan to populate your row_number.