QUERY PLAN
Limit (cost=67.74..67.77 rows=10 width=195)
-> Sort (cost=67.74..68.44 rows=278 width=195)
Sort Key: s.created_at DESC
-> HashAggregate (cost=58.95..61.73 rows=278 width=195)
Group Key: s.id, u.id
-> Nested Loop (cost=0.00..57.56 rows=278 width=195)
-> Seq Scan on tbl_users u (cost=0.00..8.16 rows=1 width=4)
Filter: ((id = 1000) AND (department_id = 10))
-> Seq Scan on tbl_tasks s (cost=0.00..46.62 rows=278 width=191)
Filter: ((parent_id IS NULL) AND (head_of = 1000))