1 启用或禁用

/usr/local/mysql/bin/mysql -uroot -p`cat /etc/sqlpass ` -P3306 -h227.0.0.1 < $BASEDIR/share/install_rewriter.sql

/usr/local/mysql/bin/mysql -uroot -p`cat /etc/sqlpass ` -P3306 -h227.0.0.1 < $BASEDIR/share/uninstall_rewriter.sql 

 

mysql> show variables like 'rewrite_%';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| rewriter_enabled | ON    |
| rewriter_verbose | 1     |
+------------------+-------+

mysql> use query_rewrite;
mysql> show tables;
+-------------------------+
| Tables_in_query_rewrite |
+-------------------------+
| rewrite_rules           |
+-------------------------+
1 row in set (0.00 sec)

[mysqld]
rewriter_enabled=ON

2 简单练习

mysql> insert into rewrite_rules(pattern,pattern_database,replacement) values('select ?','test','select ?+1');
mysql> call flush_rewrite_rules();

mysql> select 1;
+-----+
| 1+1 |
+-----+
|   2 |
+-----+

3 去除类型转换

mysql> show create table tb\G;
*************************** 1. row ***************************
       Table: tb
Create Table: CREATE TABLE `tb` (
  `id` int(10) DEFAULT NULL,
  `name` varchar(20) DEFAULT NULL,
) ENGINE=InnoDB DEFAULT CHARSET=utf8


mysql> select * from tb;
+------+----------+
| id   | name     |
+------+----------+
|    1 | 12345678 |
|    1 | 12345671 |
|    1 | 12345672 |
|    1 | 12345673 |
|    1 | 12345674 |
|    1 | 12345675 |
|    1 | 12345676 |
|    1 | 12345677 |
|    1 | 12345679 |
+------+----------+

mysql> explain select * from tb where name=12345677;
+----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------------+
|  1 | SIMPLE      | tb    | NULL       | ALL  | idx_name      | NULL | NULL    | NULL |    9 |    11.11 | Using where |
+----+-------------+-------+------------+------+---------------+------+---------+------+------+----------+-------------+

mysql> insert into rewrite_rules(pattern,pattern_database,replacement) values("select * from tb where name=?","test","select * from tb where name = cast(? as char character set utf8)");
Query OK, 1 row affected (0.08 sec)
思考：为什么不直接写？替换为‘？’ ，因为？如果被单引号包起来就失效了！

mysql> call flush_rewrite_rules();
Query OK, 0 rows affected (0.09 sec)

mysql> select * from tb where name=12345678;
mysql> show warnings;
+-------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                                                       |
+-------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Note  | 1105 | Query 'select * from tb where name=12345678' rewritten to 'select * from tb where name = cast(12345678 as char character set utf8)' by a query rewrite plugin |
+-------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

4 改字段名后兼容报错

mysql> select * from tb where uid=1;
ERROR 1054 (42S22): Unknown column 'uid' in 'where clause'

mysql> insert into rewrite_rules(pattern,pattern_database,replacement) values("select * from tb where uid=?","test","select * from tb where id=?");
Query OK, 1 row affected (0.06 sec)

mysql> call flush_rewrite_rules();
Query OK, 0 rows affected (0.06 sec)