QUERY PLAN
Aggregate (cost=79.99..80.00 rows=1 width=8)
-> Sort (cost=76.15..76.79 rows=256 width=228)
Sort Key: s.created_at DESC
-> HashAggregate (cost=63.35..65.91 rows=256 width=228)
Group Key: s.id, u.id
-> Nested Loop (cost=0.00..62.07 rows=256 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..51.35 rows=256 width=24)
Filter: ((parent_id IS NULL) AND (head_of = 1000) AND (status = '1'::smallint))