QUERY PLAN
Limit (cost=57.53..57.54 rows=5 width=198)
-> Sort (cost=57.53..57.54 rows=5 width=198)
Sort Key: s.status, u.pinyin_shortcut, s.target_completed_at, s.updated_at DESC
-> Group (cost=57.44..57.47 rows=5 width=198)
Group Key: s.id, u.id
-> Sort (cost=57.44..57.45 rows=5 width=198)
Sort Key: s.id, u.id
-> Hash Left Join (cost=9.24..57.38 rows=5 width=198)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..48.12 rows=5 width=191)
Filter: ((parent_id IS NULL) AND (task_group_id = 211))
-> Hash (cost=7.44..7.44 rows=144 width=7)
-> Seq Scan on tbl_users u (cost=0.00..7.44 rows=144 width=7)