2019独角兽企业重金招聘Python工程师标准>>> 
1. 方案示意图
2. 创建物理库
以root账号登录mariaDB, 创建三个schema: db_10001、db_10013、db_10020， 分别用来存放商户10001、10013、10020的数据:
C:\Users\HuQingmiao>mysql -uroot -p123456
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 3
Server version: 10.1.16-MariaDB mariadb.org binary distribution
Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> create database db_10001;
Query OK, 1 row affected (0.00 sec)
MariaDB [(none)]> create database db_10013;
Query OK, 1 row affected (0.00 sec)
MariaDB [(none)]> create database db_10020;
Query OK, 1 row affected (0.00 sec)
在以上三个schema上分别执行建表语句（也可以在配置mycat 逻辑库后通过mycat执行）:
DROP TABLE if EXISTS tenant_user;
CREATE TABLE tenant_user
(
id BIGINT UNSIGNED NOT NULL,
-- tenant_id INT(10) NOT NULL , //注意，不需要此列
name VARCHAR(255) NOT NULL ,
mbl_nbr VARCHAR(15) NOT NULL ,
idcard_no VARCHAR(15),
gender CHAR (1),
PRIMARY KEY(id)
) ;
DROP TABLE if EXISTS dict ;
CREATE TABLE dict
(
id BIGINT UNSIGNED AUTO_INCREMENT NOT NULL,
kind VARCHAR(30) not null comment '类别',
kind_desc VARCHAR(45) comment '类别描述',
code VARCHAR(30) not null comment '编码',
name VARCHAR(250) not null comment '名称',
order_by SMALLINT not null comment '排序号',
status SMALLINT not null comment '0-作废 1-有效',
PRIMARY KEY (id)
);
注意， 对于需要水平切分的表，不能设置自增主键，否则不同结点会存在相同主键值； 另外，对于global类型的表，也最好不用要自增主键，并发时会造成冲键冲突。
3. 配置逻辑库
按上图，打开${MYCAT_HOME}/conf/schema.xml，创建三个逻辑库、配置相应的datanode：
打开${MYCAT_HOME}/conf/server.xml，给用户root授权三个逻辑库的权限：
123456
TESTDB,logic_10001,logic_10013,logic_10020
4. 读写测试
重启、并登录mycat：
C:\Users\HuQingmiao>mycat restart
wrapper | Stopping the Mycat-server service...
wrapper | Mycat-server stopped.
wrapper | Starting the Mycat-server service...
wrapper | Mycat-server started.
C:\Users\HuQingmiao>mysql -uroot -p123456 -hlocalhost -P8066 -DTESTDB
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.29-mycat-1.6-RELEASE-20161028204710 MyCat Server (OpenCloundDB)
Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
写入数据， 注意 要在原生sql前加上注解以告诉mycat操作哪个逻辑库，即：
/*!mycat:schema = 逻辑库 */ 原生sql
执行下列脚本：
/*!mycat:schema = logic_10001 */
insert into tenant_user (id, name, mbl_nbr, idcard_no )
values (1, '牟森林', '13223232532', null);
/*!mycat:schema = logic_10013 */
insert into tenant_user (id, name, mbl_nbr, idcard_no )
values (2, '牟森林', '13223232532', null);
/*!mycat:schema = logic_10020 */
insert into tenant_user (id, name, mbl_nbr, idcard_no )
values (3, '胡三', '13520235368', null);
/*!mycat:schema = logic_10001 */
insert into dict (id, kind, kind_desc, code, name, order_by,status )
values (1,'tenant_entp_status', '企业信息状态', '1', '待认证', 1, 1);
/*!mycat:schema = logic_10001 */
insert into dict (id,kind, kind_desc, code, name, order_by,status )
values (3,'tenant_entp_status', '企业信息状态', '5', '已认证', 5, 1);
commit;
查看数据:
MySQL [TESTDB]> /*!mycat:schema = logic_10001 */
-> SELECT * FROM tenant_user;
+----+--------+-------------+-----------+--------+
| id | name | mbl_nbr | idcard_no | gender |
+----+--------+-------------+-----------+--------+
| 1 | 牟森林 | 13223232532 | NULL | NULL |
+----+--------+-------------+-----------+--------+
1 row in set (0.00 sec)
MySQL [TESTDB]> /*!mycat:schema =logic_10001 */
-> SELECT * FROM dict;
+----+--------------------+--------------+------+----------+----------+--------+
| id | kind | kind_desc | code | name | order_by | status |
+----+--------------------+--------------+------+----------+----------+--------+
| 1 | tenant_entp_status | 企业信息状态 | 1 | 待认证 | 1 | 1 |
| 3 | tenant_entp_status | 企业信息状态 | 5 | 已认证 | 5 | 1 |
+----+--------------------+--------------+------+----------+----------+--------+
3 rows in set (0.00 sec)
MySQL [TESTDB]> /*!mycat:schema =logic_10013 */
-> SELECT * FROM tenant_user;
+----+--------+-------------+-----------+--------+
| id | name | mbl_nbr | idcard_no | gender |
+----+--------+-------------+-----------+--------+
| 2 | 牟森林 | 13223232532 | NULL | NULL |
+----+--------+-------------+-----------+--------+
1 row in set (0.00 sec)
MySQL [TESTDB]> /*!mycat:schema =logic_10013 */
-> SELECT * FROM dict;
+----+--------------------+--------------+------+----------+----------+--------+
| id | kind | kind_desc | code | name | order_by | status |
+----+--------------------+--------------+------+----------+----------+--------+
| 1 | tenant_entp_status | 企业信息状态 | 1 | 待认证 | 1 | 1 |
| 3 | tenant_entp_status | 企业信息状态 | 5 | 已认证 | 5 | 1 |
+----+--------------------+--------------+------+----------+----------+--------+
3 rows in set (0.00 sec)
MySQL [TESTDB]> /*!mycat:schema = logic_10020 */
-> SELECT * FROM tenant_user;
+----+------+-------------+-----------+--------+
| id | name | mbl_nbr | idcard_no | gender |
+----+------+-------------+-----------+--------+
| 3 | 胡三 | 13520235368 | NULL | NULL |
+----+------+-------------+-----------+--------+
1 row in set (0.00 sec)
MySQL [TESTDB]> /*!mycat:schema = logic_10020 */
-> SELECT * FROM dict;
+----+--------------------+--------------+------+----------+----------+--------+
| id | kind | kind_desc | code | name | order_by | status |
+----+--------------------+--------------+------+----------+----------+--------+
| 1 | tenant_entp_status | 企业信息状态 | 1 | 待认证 | 1 | 1 |
| 3 | tenant_entp_status | 企业信息状态 | 5 | 已认证 | 5 | 1 |
+----+--------------------+--------------+------+----------+----------+--------+
3 rows in set (0.00 sec)
5. 验证切分效果
现在登录本地mariaDB各个物理库，检查数据分布：
C:\Users\HuQingmiao>mysql -uroot -p123456
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 614
Server version: 10.1.16-MariaDB mariadb.org binary distribution
Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> select * from db_10001.tenant_user;
+----+-----------+--------+-------------+-----------+--------+
| id | tenant_id | name | mbl_nbr | idcard_no | gender |
+----+-----------+--------+-------------+-----------+--------+
| 1 | 10001 | 牟森林 | 13223232532 | NULL | NULL |
+----+-----------+--------+-------------+-----------+--------+
1 row in set (0.00 sec)
MariaDB [(none)]> select * from db_10001.dict;
+----+--------------------+--------------+------+----------+----------+--------+
| id | kind | kind_desc | code | name | order_by | status |
+----+--------------------+--------------+------+----------+----------+--------+
| 1 | tenant_entp_status | 企业信息状态 | 1 | 待认证 | 1 | 1 |
| 3 | tenant_entp_status | 企业信息状态 | 5 | 已认证 | 5 | 1 |
+----+--------------------+--------------+------+----------+----------+--------+
3 rows in set (0.00 sec)
MariaDB [(none)]> select * from db_10013.tenant_user;
+----+-----------+--------+-------------+-----------+--------+
| id | tenant_id | name | mbl_nbr | idcard_no | gender |
+----+-----------+--------+-------------+-----------+--------+
| 2 | 10013 | 牟森林 | 13223232532 | NULL | NULL |
+----+-----------+--------+-------------+-----------+--------+
1 row in set (0.00 sec)
MariaDB [(none)]> select * from db_10013.dict;
+----+--------------------+--------------+------+----------+----------+--------+
| id | kind | kind_desc | code | name | order_by | status |
+----+--------------------+--------------+------+----------+----------+--------+
| 1 | tenant_entp_status | 企业信息状态 | 1 | 待认证 | 1 | 1 |
| 3 | tenant_entp_status | 企业信息状态 | 5 | 已认证 | 5 | 1 |
+----+--------------------+--------------+------+----------+----------+--------+
3 rows in set (0.00 sec)
6. 修改应用程序
接下来，要对应用程序做以下两处修改：
1） 引入类TenantContextHolder.java， 然后在受理请求的方法中， 在接收入参后、处理业务前， 加上一行代码以把租户id暂存到当前线程变量（ThreadLocal）中， 并且在处理完成、返回给调用者前， 把租户id从当前线程变量中移除，代码如下：
public String realriskEventDecision（Long tenantId, Long appId, String event）{
// 把租户id暂存到 ThreadLocal
TenantContextHolder.setTenant(tenant);
// 处理业务逻辑
do some business..
// 把租户id从 ThreadLocal移除
TenantContextHolder.remove();
return ..
}
2） 引入TenantSQLInterceptor类， 在mybatis配置文件中，增加以下内容：
TenantSQLInterceptor将拦截sql, 向其添加头部注解， 以标明该sql应该发往哪个逻辑库执行； 它会调用TenantContextHolder.getSchema()以获得逻辑库名。
7. 方案总结
本方案适合把已有系统升级为saas服务， 只需要修改少量的代码， 即通过aop在请求入口处记录tenant_id，再通过sql拦截器获取tenant_id对应的逻辑库，然后在sql 头部添加mycat特有的注解以指明在哪个逻辑库执行。