QUERY PLAN
Limit (cost=56.30..56.32 rows=9 width=195)
-> Sort (cost=56.30..56.32 rows=9 width=195)
Sort Key: s.created_at
-> Group (cost=56.09..56.16 rows=9 width=195)
Group Key: s.id, u.id
-> Sort (cost=56.09..56.11 rows=9 width=195)
Sort Key: s.id, u.id
-> Hash Join (cost=8.07..55.95 rows=9 width=195)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..47.73 rows=57 width=191)
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)