QUERY PLAN
Group (cost=9.76..9.77 rows=1 width=4)
Group Key: client_id
-> Sort (cost=9.76..9.77 rows=1 width=4)
Sort Key: client_id
-> Seq Scan on tbl_user_visit_clients (cost=0.00..9.75 rows=1 width=4)
Filter: (user_id = 1001)