QUERY PLAN
Limit (cost=58.48..58.50 rows=10 width=195)
-> Sort (cost=58.45..58.56 rows=42 width=195)
Sort Key: s.created_at
-> HashAggregate (cost=56.91..57.34 rows=42 width=195)
Group Key: s.id, u.id
-> Nested Loop (cost=0.00..56.70 rows=42 width=195)
-> Seq Scan on tbl_users u (cost=0.00..8.16 rows=1 width=4)
Filter: ((id = 1001) AND (department_id = 4))
-> Seq Scan on tbl_tasks s (cost=0.00..48.12 rows=42 width=191)
Filter: ((parent_id IS NULL) AND (head_of = 1001))