QUERY PLAN
Limit (cost=59.19..59.21 rows=9 width=196)
-> Sort (cost=59.19..59.21 rows=9 width=196)
Sort Key: s.created_at
-> Group (cost=58.98..59.05 rows=9 width=196)
Group Key: s.id, u.id
-> Sort (cost=58.98..59.00 rows=9 width=196)
Sort Key: s.id
-> Nested Loop (cost=0.00..58.84 rows=9 width=196)
-> 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..50.59 rows=9 width=192)
Filter: ((parent_id IS NULL) AND (head_of = 1000) AND (status = '0'::smallint))