QUERY PLAN
Limit (cost=64.27..64.28 rows=5 width=207)
-> Sort (cost=64.27..64.28 rows=5 width=207)
Sort Key: s.status, u.pinyin_shortcut, s.target_completed_at, s.updated_at DESC
-> Group (cost=64.17..64.21 rows=5 width=207)
Group Key: s.id, u.id
-> Sort (cost=64.17..64.19 rows=5 width=207)
Sort Key: s.id, u.id
-> Hash Left Join (cost=18.24..64.12 rows=5 width=207)
Hash Cond: (s.head_of = u.id)
-> Seq Scan on tbl_tasks s (cost=0.00..45.86 rows=5 width=200)
Filter: ((parent_id IS NULL) AND (task_group_id = 203))
-> Hash (cost=16.44..16.44 rows=144 width=7)
-> Seq Scan on tbl_users u (cost=0.00..16.44 rows=144 width=7)