QUERY PLAN
Limit (cost=57.95..57.95 rows=1 width=195)
-> Sort (cost=57.95..57.95 rows=1 width=195)
Sort Key: s.created_at
-> Group (cost=57.93..57.94 rows=1 width=195)
Group Key: s.id, u.id
-> Sort (cost=57.93..57.93 rows=1 width=195)
Sort Key: s.id
-> Nested Loop (cost=0.00..57.92 rows=1 width=195)
-> Seq Scan on tbl_tasks s (cost=0.00..49.75 rows=1 width=191)
Filter: ((parent_id IS NULL) AND (head_of = 1001) AND (status = '0'::smallint))
-> Seq Scan on tbl_users u (cost=0.00..8.16 rows=1 width=4)
Filter: ((id = 1001) AND (department_id = 4))