QUERY PLAN
Limit (cost=58.42..58.44 rows=10 width=198)
-> Sort (cost=58.42..58.58 rows=65 width=198)
Sort Key: s.status, u.pinyin_shortcut, s.target_completed_at, s.updated_at DESC
-> HashAggregate (cost=56.36..57.01 rows=65 width=198)
Group Key: s.id, u.id
-> Hash Left Join (cost=9.24..56.04 rows=65 width=198)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..46.62 rows=65 width=191)
Filter: ((parent_id IS NULL) AND (task_group_id = 106))
-> 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)