优化阻塞数据库的 MySQL DELETE 查询

Question

我需要关于优化以下 mysql 删除查询的建议：

$group_id = '1234';

     // DELETE GROUP DISCUSSION POSTS 
        mysql_query("DELETE FROM table_groupposts 
                     WHERE grouppost_grouptopic_id 
                     IN (SELECT grouptopic_id from table_grouptopics 
                         WHERE grouptopic_group_id='{$group_id}')
                    ");

echo "DEL groupposts: " . mysql_affected_rows() . "<br />";

拥有一个大型数据库，运行查询最多需要 70 秒，即使没有讨论帖子。

有什么办法可以加快这个过程吗？

Answer 1

为什么删除操作不使用连接而不是子查询

delete tg from table_groupposts tg
join table_grouptopics gt on gt.grouptopic_id = tg.grouppost_grouptopic_id
where gt.grouptopic_group_id='$group_id'

确保连接键已编入索引，如果没有则按

alter table table_groupposts add index grouppost_grouptopic_id_idx(grouppost_grouptopic_id);

alter table table_grouptopics add index grouptopic_id_idx(grouptopic_id);

最后

alter table table_grouptopics add index grouptopic_group_id_idx(grouptopic_group_id)

优化阻塞数据库的 MySQL DELETE 查询

Optimizing a MySQL DELETE Query which is blocking the database

php

mysql

innodb

sql-delete