QUERY PLAN
Aggregate (cost=56.24..56.25 rows=1 width=8)
-> Sort (cost=56.12..56.14 rows=8 width=228)
Sort Key: s.created_at
-> Group (cost=55.94..56.00 rows=8 width=228)
Group Key: s.id, u.id
-> Sort (cost=55.94..55.96 rows=8 width=16)
Sort Key: s.id, u.id
-> Hash Join (cost=8.07..55.82 rows=8 width=16)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..47.61 rows=51 width=24)
Filter: ((parent_id IS NULL) AND (status = '0'::smallint))
-> Hash (cost=7.80..7.80 rows=22 width=4)
-> Seq Scan on tbl_users u (cost=0.00..7.80 rows=22 width=4)
Filter: (department_id = 10)