mysql查询速度慢，加入庞大的表，不使用索引

Question

SELECT archive.id, archive.file, archive.create_timestamp, archive.spent 
FROM archive LEFT JOIN submissions ON archive.id = submissions.id
WHERE submissions.id is NULL 
AND archive.file is not NULL 
AND archive.create_timestamp < DATE_SUB(NOW(), INTERVAL 6 month) 
AND spent = 0 
ORDER BY archive.create_timestamp ASC LIMIT 10000

EXPLAIN结果：

+----+-------------+--------------------+--------+--------------------------------+------------------+---------+--------------------------------------------+-----------+--------------------------------------+
| id | select_type | table              | type   | possible_keys                  | key              | key_len | ref                                        | rows      | Extra                                |
+----+-------------+--------------------+--------+--------------------------------+------------------+---------+--------------------------------------------+-----------+--------------------------------------+
|  1 | SIMPLE      | archive            | range  | create_timestamp,file_in       | create_timestamp | 4       | NULL                                       | 111288502 | Using where                          |
|  1 | SIMPLE      | submissions        | eq_ref | PRIMARY                        | PRIMARY          | 4       | production.archive.id                      |         1 | Using where; Using index; Not exists |
+----+-------------+--------------------+--------+--------------------------------+------------------+---------+--------------------------------------------+-----------+--------------------------------------+

我已经尝试过使用索引来存档表：

USE INDEX (create_timestamp,file_in)

归档表很大，约有150万条记录。

非常感谢任何有关加快此查询的帮助。

Answer 1

您想要使用复合索引。对于此查询：

create index archive_file_spent_createts on archive(file, spent, createtimestamp);

在这样的索引中，您希望where条件=首先出现，然后是最多一列不等式。在这种情况下，我不确定MySQL是否会使用order by的索引。

这假设where条件确实会显着减小数据的大小。