MySQL-如何添加；使用连接缓冲区（块嵌套循环）"；问什么？

当我在笔记本电脑上运行一个查询时，执行起来需要一秒钟的时间，但在生产环境中，查询会持续57秒（它会使应用程序崩溃——这是用Ruby on Rails编写的）

我用EXPLAIN运行了这个查询，发现在我的笔记本电脑上执行的查询中有一个表

使用联接缓冲区（块嵌套循环）

但这在生产中是缺失的（对于此表，EXTRA列中没有任何内容）

为什么呢？如何使用连接缓冲区（块嵌套循环）将添加到生产中

多谢各位

编辑：以下是查询：

SELECT `shippers`.`company_name` 
FROM `shippers` 
LEFT OUTER JOIN `shipper_services` 
ON `shipper_services`.`shipper_id` = `shippers`.`id` 
LEFT OUTER JOIN `services` ON `services`.`id` = `shipper_services`.`service_id` 
LEFT OUTER JOIN `shipper_freight_flow_industries` 
ON `shipper_freight_flow_industries`.`shipper_id` = `shippers`.`id` 
LEFT OUTER JOIN `freight_flow_industries` 
ON `freight_flow_industries`.`id` = `shipper_freight_flow_industries`.`freight_flow_industry_id` 
WHERE `shippers`.`id` IN (189459, 337334, 149804, 36046, 158403, 165682, 153399, 51471, 211796, 164984, 61118, 56497, 340353, 66525, 225635, 250376, 33237, 69140, 151777, 169530, 245255, 142246, 259597, 57889, 262986, 167803, 33459, 40561, 65878, 44356, 169545, 210358, 25555, 4563, 82538, 157765, 232509, 213248, 37380, 258965, 340616, 340926, 143314, 195553, 60845, 161463, 255789, 38942, 192219, 811, 64672, 13530, 340809, 66030, 157223, 347671, 176886, 157812, 348255, 37357, 337003, 5588, 24257, 164799, 230717, 153801, 171835, 66595, 176780, 250184, 3262, 201519, 223904, 241992, 254167, 242449, 5368, 23903, 52571, 7198, 40135, 340494, 11851, 171285, 26810, 231003, 193961, 341161, 17122, 56660, 348103, 145539, 176912, 19716, 196617, 34803, 75444, 62418, 149606, 158879, 242439, 63291, 80548, 170778, 184871, 254549, 337109, 151159, 255077, 38939, 191926, 337720, 205999, 247471, 258106, 40225, 52599, 141637, 207246, 247541, 258876, 52629, 65936, 164884, 192238, 247588, 13669, 26875, 41763, 52700, 143009, 154515, 174092, 192869, 210753, 248501, 13835, 27222, 43017, 52995, 154640, 165368, 176390, 235034, 248829, 261492, 16610, 29589, 43109, 143661, 195373, 211866, 236874, 33148, 67629, 145474, 166592, 212358, 236937, 263276, 353, 18193, 44479, 68389, 196133, 241530, 251862, 331361, 770, 45861, 68982, 145652, 157945, 177022, 214534, 241659, 253705, 332487, 349455, 20303, 46852, 61001, 147373, 158198, 178036, 200139, 220189, 241765, 253987, 334046, 350465, 21532, 46970, 149478, 170761, 178187, 334167, 350466, 3285, 22934, 48334, 77067, 170770, 184809, 201905, 224892, 254293, 23063, 51366, 203181, 37607, 63370, 80720, 163426, 170798, 203424, 226486, 243809, 244904, 63388, 81420, 163553, 170800, 203819, 228767, 244936, 6057, 24664, 52584, 152229, 164080, 170812, 192096, 229759, 257935, 25300, 52592, 65635, 82575, 152798, 164171, 170817, 192179, 206647, 229772) 
AND ((
          (ACOS(least(1,COS(0.5194174327134307)*COS(-1.664517065837707)*COS(RADIANS(shippers.latitude))*COS(RADIANS(shippers.longitude))+
          COS(0.5194174327134307)*SIN(-1.664517065837707)*COS(RADIANS(shippers.latitude))*SIN(RADIANS(shippers.longitude))+
          SIN(0.5194174327134307)*SIN(RADIANS(shippers.latitude))))*3963.1899999999996)
          <= 5.0)) AND (store_location = "0" AND corporate_hq = "0" AND queued_item="0") 
GROUP BY company_name  ORDER BY count_of_facilities DESC)

索引：

+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table                           | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| shipper_freight_flow_industries |          0 | PRIMARY  |            1 | id          | A         |      241609 |     NULL | NULL   |      | BTREE      |         |               |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table                           | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| shipper_freight_flow_industries |          0 | PRIMARY  |            1 | id          | A         |          58 |     NULL | NULL   |      | BTREE      |         |               |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

本地主机：

+----+-------------+---------------------------------+--------+-------------------+-----------+---------+-----------------------------------------------------------------------------------+------+----------------------------------------------------+
| id | select_type | table                           | type   | possible_keys     | key       | key_len | ref                                                                               | rows | Extra                                              |
+----+-------------+---------------------------------+--------+-------------------+-----------+---------+-----------------------------------------------------------------------------------+------+----------------------------------------------------+
|  1 | SIMPLE      | shippers                        | range  | PRIMARY,idx_store | PRIMARY   | 4       | NULL                                                                              |  245 | Using where; Using temporary; Using filesort       |
|  1 | SIMPLE      | shipper_services                | ref    | idx_combo         | idx_combo | 5       | development.shippers.id                                              |    2 | Using index                                        |
|  1 | SIMPLE      | services                        | eq_ref | PRIMARY           | PRIMARY   | 4       | development.shipper_services.service_id                              |    1 | Using index                                        |
|  1 | SIMPLE      | shipper_freight_flow_industries | ALL    | NULL              | NULL      | NULL    | NULL                                                                              |   58 | Using where; Using join buffer (Block Nested Loop) |
|  1 | SIMPLE      | freight_flow_industries         | eq_ref | PRIMARY           | PRIMARY   | 4       | development.shipper_freight_flow_industries.freight_flow_industry_id |    1 | Using index                                        |
+----+-------------+---------------------------------+--------+-------------------+-----------+---------+-----------------------------------------------------------------------------------+------+----------------------------------------------------+

索引：

+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table                           | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| shipper_freight_flow_industries |          0 | PRIMARY  |            1 | id          | A         |      241609 |     NULL | NULL   |      | BTREE      |         |               |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table                           | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| shipper_freight_flow_industries |          0 | PRIMARY  |            1 | id          | A         |          58 |     NULL | NULL   |      | BTREE      |         |               |
+---------------------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

---

这篇文章确实提出了两个问题

隐式查询类似于“如何在我的生产系统上提高此查询的性能？”。
正如@mummercor已经注意到的，答案是“在

shipper\u id

上添加一个索引到

shipper\u freight\u flow\u industries

表中”，这是推荐的方法，只要由于所涉及表的大小，连接创建大量组合

关于明确的一点：

为什么呢？如何使用连接缓冲区（块嵌套循环）将添加到生产中

时间差明显来自于

托运人(shipper)货运(flow)行业

表的大小表：笔记本电脑数据库为58，生产数据库为241609

只有笔记本电脑使用连接缓冲区这一事实可能是由于

join\u buffer\u size

变量（请看）：在两个系统上，它可能都设置为默认值（256K）。
所以它被用在笔记本电脑数据库上，但在生产系统上，它太小，不允许使用它来处理所涉及的行数

如上所述，添加索引是提高此查询性能的首选方法，但尝试在没有索引的情况下使用非常大的

join\u buffer\u size

，并比较结果可能会很有趣。
在某些特殊情况下，此解决方案可能是一个很好的替代方案，例如，如果此索引除了用于此查询之外没有其他用途，而且它还驻留了其他任务，如表更新。

这是Mysql的一个错误

您可以使用

set optimizer_switch='block_nested_loop=off'

---

不知道为什么会发生这种情况，但也许您可以在

shipper\u freight\u flow\u industries

中添加带有

shipper\u id

的索引，请提供shipper\u freight\u flow\u industries表中的索引@添加了阴影，谢谢。另外，

分析表

可能会有帮助。请尝试@mummercor的建议并添加索引。