如何在大表上使用 LEFT JOIN 优化非常慢的 SELECT

如何解决如何在大表上使用 LEFT JOIN 优化非常慢的 SELECT

选择一些要包含在person. 以几种组合对它们进行索引——使用复合索引，而不是单列索引。

这本质上是摆脱 EAV-sucks-at-performance 的唯一出路，这就是您所在的位置。

解决方法

我在谷歌上搜索，自学并寻找解决方案几个小时，但没有运气。我在这里发现了一些类似的问题，但不是这种情况。

我的表：

persons (~10M rows)
attributes (location,age,…)
links (M:M) between persons and attributes (~40M rows)

情况： 我尝试person_id从某些位置（）中选择所有人员 id（ location.attribute_value BETWEEN 3000 AND 7000），具有某种性别（gender.attribute_value = 1），出生于某些年份（bornyear.attribute_value BETWEEN 1980 AND 2000）并具有某种眼睛的颜色（eyecolor.attribute_value IN (2,3)）。

这是我的查询女巫需要3~4 分钟。我想优化：

SELECT person_id
FROM person
    LEFT JOIN attribute location ON location.attribute_type_id = 1 AND location.person_id = person.person_id
    LEFT JOIN attribute gender ON gender.attribute_type_id = 2 AND gender.person_id = person.person_id
    LEFT JOIN attribute bornyear ON bornyear.attribute_type_id = 3 AND bornyear.person_id = person.person_id
    LEFT JOIN attribute eyecolor ON eyecolor.attribute_type_id = 4 AND eyecolor.person_id = person.person_id
WHERE 1
    AND location.attribute_value BETWEEN 3000 AND 7000
    AND gender.attribute_value = 1
    AND bornyear.attribute_value BETWEEN 1980 AND 2000
    AND eyecolor.attribute_value IN (2,3)
LIMIT 100000;

结果：

+-----------+
| person_id |
+-----------+
|       233 |
|       605 |
|       ... |
|   8702599 |
|   8703617 |
+-----------+
100000 rows in set (3 min 42.77 sec)

解释扩展：

+----+-------------+----------+--------+---------------------------------------------+-----------------+---------+--------------------------+---------+----------+--------------------------+
| id | select_type | table    | type   | possible_keys                               | key             | key_len | ref                      | rows    | filtered | Extra                    |
+----+-------------+----------+--------+---------------------------------------------+-----------------+---------+--------------------------+---------+----------+--------------------------+
|  1 | SIMPLE      | bornyear | range  | attribute_type_id,attribute_value,person_id | attribute_value | 5       | NULL                     | 1265229 |   100.00 | Using where              |
|  1 | SIMPLE      | location | ref    | attribute_type_id,person_id | person_id       | 5       | test1.bornyear.person_id |       4 |   100.00 | Using where              |
|  1 | SIMPLE      | eyecolor | ref    | attribute_type_id,person_id | person_id       | 5       | test1.bornyear.person_id |       4 |   100.00 | Using where              |
|  1 | SIMPLE      | gender   | ref    | attribute_type_id,person_id | person_id       | 5       | test1.eyecolor.person_id |       4 |   100.00 | Using where              |
|  1 | SIMPLE      | person   | eq_ref | PRIMARY                                     | PRIMARY         | 4       | test1.location.person_id |       1 |   100.00 | Using where; Using index |
+----+-------------+----------+--------+---------------------------------------------+-----------------+---------+--------------------------+---------+----------+--------------------------+
5 rows in set,1 warning (0.02 sec)

分析：

+------------------------------+-----------+
| Status                       | Duration  |
+------------------------------+-----------+
| Sending data                 |  3.069452 |
| Waiting for query cache lock |  0.000017 |
| Sending data                 |  2.968915 |
| Waiting for query cache lock |  0.000019 |
| Sending data                 |  3.042468 |
| Waiting for query cache lock |  0.000043 |
| Sending data                 |  3.264984 |
| Waiting for query cache lock |  0.000017 |
| Sending data                 |  2.823919 |
| Waiting for query cache lock |  0.000038 |
| Sending data                 |  2.863903 |
| Waiting for query cache lock |  0.000014 |
| Sending data                 |  2.971079 |
| Waiting for query cache lock |  0.000020 |
| Sending data                 |  3.053197 |
| Waiting for query cache lock |  0.000087 |
| Sending data                 |  3.099053 |
| Waiting for query cache lock |  0.000035 |
| Sending data                 |  3.064186 |
| Waiting for query cache lock |  0.000017 |
| Sending data                 |  2.939404 |
| Waiting for query cache lock |  0.000018 |
| Sending data                 |  3.440288 |
| Waiting for query cache lock |  0.000086 |
| Sending data                 |  3.115798 |
| Waiting for query cache lock |  0.000068 |
| Sending data                 |  3.075427 |
| Waiting for query cache lock |  0.000072 |
| Sending data                 |  3.658319 |
| Waiting for query cache lock |  0.000061 |
| Sending data                 |  3.335427 |
| Waiting for query cache lock |  0.000049 |
| Sending data                 |  3.319430 |
| Waiting for query cache lock |  0.000061 |
| Sending data                 |  3.496563 |
| Waiting for query cache lock |  0.000029 |
| Sending data                 |  3.017041 |
| Waiting for query cache lock |  0.000032 |
| Sending data                 |  3.132841 |
| Waiting for query cache lock |  0.000050 |
| Sending data                 |  2.901310 |
| Waiting for query cache lock |  0.000016 |
| Sending data                 |  3.107269 |
| Waiting for query cache lock |  0.000062 |
| Sending data                 |  2.937373 |
| Waiting for query cache lock |  0.000016 |
| Sending data                 |  3.097082 |
| Waiting for query cache lock |  0.000261 |
| Sending data                 |  3.026108 |
| Waiting for query cache lock |  0.000026 |
| Sending data                 |  3.089760 |
| Waiting for query cache lock |  0.000041 |
| Sending data                 |  3.012763 |
| Waiting for query cache lock |  0.000021 |
| Sending data                 |  3.069694 |
| Waiting for query cache lock |  0.000046 |
| Sending data                 |  3.591908 |
| Waiting for query cache lock |  0.000060 |
| Sending data                 |  3.526693 |
| Waiting for query cache lock |  0.000076 |
| Sending data                 |  3.772659 |
| Waiting for query cache lock |  0.000069 |
| Sending data                 |  3.346089 |
| Waiting for query cache lock |  0.000245 |
| Sending data                 |  3.300460 |
| Waiting for query cache lock |  0.000019 |
| Sending data                 |  3.135361 |
| Waiting for query cache lock |  0.000021 |
| Sending data                 |  2.909447 |
| Waiting for query cache lock |  0.000039 |
| Sending data                 |  3.337561 |
| Waiting for query cache lock |  0.000140 |
| Sending data                 |  3.138180 |
| Waiting for query cache lock |  0.000090 |
| Sending data                 |  3.060687 |
| Waiting for query cache lock |  0.000085 |
| Sending data                 |  2.938677 |
| Waiting for query cache lock |  0.000041 |
| Sending data                 |  2.977974 |
| Waiting for query cache lock |  0.000872 |
| Sending data                 |  2.918640 |
| Waiting for query cache lock |  0.000036 |
| Sending data                 |  2.975842 |
| Waiting for query cache lock |  0.000051 |
| Sending data                 |  2.918988 |
| Waiting for query cache lock |  0.000021 |
| Sending data                 |  2.943810 |
| Waiting for query cache lock |  0.000061 |
| Sending data                 |  3.330211 |
| Waiting for query cache lock |  0.000025 |
| Sending data                 |  3.411236 |
| Waiting for query cache lock |  0.000023 |
| Sending data                 | 23.339035 |
| end                          |  0.000807 |
| query end                    |  0.000023 |
| closing tables               |  0.000325 |
| freeing items                |  0.001217 |
| logging slow query           |  0.000007 |
| logging slow query           |  0.000011 |
| cleaning up                  |  0.000104 |
+------------------------------+-----------+
100 rows in set (0.00 sec)

表结构：

CREATE TABLE `attribute` (
  `attribute_id` int(11) unsigned NOT NULL AUTO_INCREMENT,`attribute_type_id` int(11) unsigned DEFAULT NULL,`attribute_value` int(6) DEFAULT NULL,`person_id` int(11) unsigned DEFAULT NULL,PRIMARY KEY (`attribute_id`),KEY `attribute_type_id` (`attribute_type_id`),KEY `attribute_value` (`attribute_value`),KEY `person_id` (`person_id`)
) ENGINE=MyISAM AUTO_INCREMENT=40000001 DEFAULT CHARSET=utf8;

CREATE TABLE `person` (
  `person_id` int(11) unsigned NOT NULL AUTO_INCREMENT,`person_name` text CHARACTER SET latin1,PRIMARY KEY (`person_id`)
) ENGINE=MyISAM AUTO_INCREMENT=20000001 DEFAULT CHARSET=utf8;

已在具有 SSD 和 1GB RAM 的 DigitalOcean 虚拟服务器上执行查询。

我认为数据库设计可能存在问题。你有什么建议可以更好地设计这种情况吗？还是只是调整上面的选择？

如何在大表上使用 LEFT JOIN 优化非常慢的 SELECT

如何解决如何在大表上使用 LEFT JOIN 优化非常慢的 SELECT

解决方法

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