QUERY PLAN
Aggregate (cost=56.60..56.61 rows=1 width=8)
-> Sort (cost=56.51..56.53 rows=6 width=228)
Sort Key: s.created_at
-> Group (cost=56.39..56.43 rows=6 width=228)
Group Key: s.id, u.id
-> Sort (cost=56.39..56.40 rows=6 width=16)
Sort Key: s.id, u.id
-> Hash Join (cost=8.07..56.31 rows=6 width=16)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..48.12 rows=42 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)