QUERY PLAN
Limit (cost=67.38..67.41 rows=10 width=195)
-> Sort (cost=67.28..67.70 rows=168 width=195)
Sort Key: s.created_at
-> HashAggregate (cost=60.02..61.70 rows=168 width=195)
Group Key: s.id, u.id
-> Hash Join (cost=8.07..59.18 rows=168 width=195)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..48.12 rows=1102 width=191)
Filter: ((parent_id IS NULL) AND (status = '1'::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)