[英]Optimizing MySQL self-join query
我有以下查询:
SELECT DISTINCT(a1.actor)
FROM actions a1
JOIN actions a2 ON a1.ip = a2.ip
WHERE a2.actor = 143
AND a2.ip != '0.0.0.0'
AND a2.ip != ''
AND a2.actor != a1.actor
AND a1.actor != 0
这是查询的解释:
+----+-------------+-------+-------+------------------+---------+---------+------------------+------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+------------------+---------+---------+------------------+------+--------------------------+
| 1 | SIMPLE | a2 | range | actor,ip,actorIp | actorIp | 66 | NULL | 3800 | Using where; Using index |
| 1 | SIMPLE | a1 | ref | ip | ip | 62 | formabilio.a2.ip | 11 | Using where |
+----+-------------+-------+-------+------------------+---------+---------+------------------+------+--------------------------+
即使由此看来,查询似乎没有问题,但在我的机器中,使用MyIsam大约需要69秒,而使用InnoDB则需要56秒。 该表或多或少有1000条记录。 从说明中可以看出,我在actor列,ip列甚至两个列上都表示。 我有mysql版本5.5.35。
您对为什么此查询需要这么长时间有任何想法吗? 我该如何优化?
TABLE SCAN正在对表操作的每个记录进行操作。
根据本教程: http : //www.mysqltutorial.org/mysql-self-join/
SELECT DISTINCT(a1.actor)
FROM actions a1
INNER JOIN actions a2
ON a1.ip = a2.ip AND
a1.actor <> a2.actor
WHERE a2.actor = 143
AND a2.ip <> '0.0.0.0'
AND a2.ip <> ''
AND a1.actor <> 0
试试这个(如果您还没有这样做的话)...下面的命令应该在连接字段和一些条件上创建索引
CREATE INDEX _actions_ip ON actions( ip );
CREATE INDEX _actions_actor ON actions( actor );
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