QUERY PLAN
Aggregate (cost=58.57..58.58 rows=1 width=8)
-> Sort (cost=58.42..58.44 rows=10 width=228)
Sort Key: s.created_at
-> Group (cost=58.18..58.25 rows=10 width=228)
Group Key: s.id, u.id
-> Sort (cost=58.18..58.20 rows=10 width=16)
Sort Key: s.id
-> Nested Loop (cost=0.00..58.01 rows=10 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..49.75 rows=10 width=24)
Filter: ((parent_id IS NULL) AND (head_of = 1000) AND (status = '0'::smallint))