QUERY PLAN
Aggregate (cost=77.26..77.27 rows=1 width=8)
-> Sort (cost=73.23..73.90 rows=269 width=228)
Sort Key: s.created_at
-> HashAggregate (cost=59.68..62.37 rows=269 width=228)
Group Key: s.id, u.id
-> Nested Loop (cost=0.00..58.34 rows=269 width=16)
-> 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..47.49 rows=269 width=24)
Filter: ((parent_id IS NULL) AND (head_of = 1000))