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Mycat学习实战-Mycat全局主键

发表于：2025-11-08 作者：千家信息网编辑

千家信息网最后更新 2025年11月08日，Mycat学习实战-Mycat全局主键@(学习)[mycat, mysql]Mycat学习实战-Mycat全局主键1. Mycat全局主键介绍2. Mycat全局主键方式2.1 本地文件方式2.2 本

千家信息网最后更新 2025年11月08日Mycat学习实战-Mycat全局主键

Mycat学习实战-Mycat全局主键

@(学习)[mycat, mysql]

Mycat学习实战-Mycat全局主键
1. Mycat全局主键介绍
2. Mycat全局主键方式
- 2.1 本地文件方式
- 2.2 本地时间戳方式
- 2.3 数据库方式
- 2.4 zookeeper方式

1. Mycat全局主键介绍

在分库分表的情况下，数据库自增主键无法保证自增主键的全局唯一。

全局序列号的语法符合标准SQL规范，其格式为：
next value for MYCATSEQ_XXX
MYCATSEQ_XXX 是序列号的名字，MyCAT自动创建新的序列号，免去了开发的复杂度，另外，MyCAT也提供了一个全局的序列号，名称为：MYCATSEQ_GLOBAL

注意，MYCATSEQ_必须大写才能正确识别。
MyCAT温馨提示：实践中，建议每个表用自己的序列号，序列号的命名建议为MYCATSEQ _tableName_ID_SEQ。

SQL中使用说明
自定义序列号的标识为：MYCATSEQ_XXX ,其中XXX为具体定义的sequence的名称，应用举例如下：
使用默认的全局sequence :
insert into tb1(id,name) values(next value for MYCATSEQ_GLOBAL,'tb1');
使用自定义的 sequence:
insert into tb2(id,name) values(next value for MYCATSEQ_MY1,'tb2');
获取最新的值
select next value for MYCATSEQ_xxx

2. Mycat全局主键方式

Mycat提供的全局主键方式如下：

本地文件方式：使用服务器本地磁盘文件的方式
数据库方式：使用数据库的方式
本地时间戳方式：使用时间戳方式
分布式zookeeper生成ID

2.1 本地文件方式

vim conf/server.xml

vim conf/sequence_conf.properties

#default global sequenceGLOBAL.HISIDS=GLOBAL.MINID=10001GLOBAL.MAXID=20000GLOBAL.CURID=10000# self define sequenceID_LOCAL_FILE.HISIDS=ID_LOCAL_FILE.MINID=1001ID_LOCAL_FILE.MAXID=2000ID_LOCAL_FILE.CURID=1000

以上配置文件中，自定义表名必须大写书写
HISIDS：表示使用过的历史分段(一般
无特殊需要可不配置)
MINID ：最小ID 值
MAXID ：表示最大ID 值
CURID 表示当前ID 值。
当 sequence_conf.properties的配置名字与表名一致的时候sql可以不包含ID字段（此处表名为id_local_file）

vim conf/schema.xml

                        
                                                select 1

实验验证：

[root@testA conf]# mysql -uroot -p123456 -P8066 -h 127.0.0.1 testmysql: [Warning] Using a password on the command line interface can be insecure.Welcome to the MySQL monitor.  Commands end with ; or \g.Your MySQL connection id is 3Server version: 5.6.29-mycat-1.6-RELEASE-20161028204710 MyCat Server (OpenCloundDB)Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> CREATE TABLE `id_local_file` (`id` varchar(20) NOT NULL ,`nm` varchar(60) NULL ,PRIMARY KEY (`id`));    Query OK, 0 rows affected (0.06 sec)mysql> insert into id_local_file(id,nm) values(next value for MYCATSEQ_GLOBAL,'id_local_file'); Query OK, 1 row affected (0.03 sec)mysql> insert into id_local_file(nm) values('id_local_file'); /* 插入的sql语句里没有了自增ID字段 */Query OK, 1 row affected (0.01 sec)mysql> select * from id_local_file;+-------+---------------+| id    | nm            |+-------+---------------+| 10001 | id_local_file || 1001  | id_local_file |+-------+---------------+2 rows in set (0.08 sec)mysql> select next value for MYCATSEQ_GLOBAL;+-------+| 10002 |+-------+| 10002 |+-------+1 row in set (0.00 sec)mysql>

优点：本地加载，读取速度较快，配置简单
缺点：mycat重新发布时，seq文件需要替换，集群部署无法用此方式，路由到不同的mycat上无法保证id唯一，使mycat变成了有状态的中间件。

2.2 本地时间戳方式

vim conf/server.xml

vim conf/sequence_time_conf.properties

#sequence depend on TIMEWORKID=01DATAACENTERID=01

两个属性值为：0-31 任意整数

vim conf/schema.xml

                        
                                                select 1

实验验证：

[root@testA conf]# mysql -uroot -p123456 -P8066 -h 127.0.0.1 testmysql: [Warning] Using a password on the command line interface can be insecure.Welcome to the MySQL monitor.  Commands end with ; or \g.Your MySQL connection id is 2Server version: 5.6.29-mycat-1.6-RELEASE-20161028204710 MyCat Server (OpenCloundDB)Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> CREATE TABLE `id_local_time` (`id` varchar(20) NOT NULL ,`nm` varchar(60) NULL ,PRIMARY KEY (`id`));Query OK, 0 rows affected (0.02 sec)mysql> insert into id_local_time(id,nm) values(next value for MYCATSEQ_GLOBAL,'id_local_time'); Query OK, 1 row affected (0.06 sec)mysql> insert into id_local_time(nm) values('id_local_time'); /* 插入的sql语句里没有了自增ID字段 */Query OK, 1 row affected (0.01 sec)mysql> select * from id_local_time;+--------------------+---------------+| id                 | nm            |+--------------------+---------------+| 922641363168792576 | id_local_time || 922641424359493632 | id_local_time |+--------------------+---------------+2 rows in set (0.06 sec)mysql> select next value for MYCATSEQ_GLOBAL;+--------------------+| 922641542101995520 |+--------------------+| 922641542101995520 |+--------------------+1 row in set (0.00 sec)

本地时间戳计算方式
ID= 64 位二进制 (42(毫秒)+5(机器 ID)+5(业务编码)+12(重复累加)
长度18位，因此下面提示非常重要。

注意
表字段长度必须大于等于18位

优点：不存在mycat重新发布影响seq的问题，
缺点：字段长度是18位。

2.3 数据库方式

vim conf/server.xml

vim conf/sequence_db_conf.properties

#sequence stored in datanodeGLOBAL=test1ID_DB=test1

在test1节点本地数据库添加函数和表，以下为sql内容：

DROP TABLE IF EXISTS mycat_sequence;CREATE TABLE mycat_sequence (NAME VARCHAR (50) NOT NULL,current_value INT NOT NULL,increment INT NOT NULL DEFAULT 100,PRIMARY KEY (NAME)) ENGINE = INNODB ;INSERT INTO mycat_sequence(name,current_value,increment) VALUES ('GLOBAL', 100000, 100);DROP FUNCTION IF EXISTS `mycat_seq_currval`;DELIMITER ;;CREATE  FUNCTION `mycat_seq_currval`(seq_name VARCHAR(50)) RETURNS varchar(64) CHARSET utf8    DETERMINISTICBEGIN         DECLARE retval VARCHAR(64);        SET retval="-999999999,null";          SELECT concat(CAST(current_value AS CHAR),",",CAST(increment AS CHAR) ) INTO retval           FROM mycat_sequence  WHERE name = seq_name;          RETURN retval ; END;;DELIMITER ;DROP FUNCTION IF EXISTS `mycat_seq_nextval`;DELIMITER ;;CREATE FUNCTION `mycat_seq_nextval`(seq_name VARCHAR(50)) RETURNS varchar(64) CHARSET utf8    DETERMINISTICBEGIN          UPDATE mycat_sequence                   SET current_value = current_value + increment                   WHERE name = seq_name;           RETURN mycat_seq_currval(seq_name);  END;;DELIMITER ;DROP FUNCTION IF EXISTS `mycat_seq_setval`;DELIMITER ;;CREATE FUNCTION `mycat_seq_setval`(seq_name VARCHAR(50), value INTEGER) RETURNS varchar(64) CHARSET utf8    DETERMINISTICBEGIN          UPDATE mycat_sequence                     SET current_value = value                     WHERE name = seq_name;           RETURN mycat_seq_currval(seq_name);  END;;DELIMITER ;

添加过程：

[root@testA mycat]# mysql -uroot -p123456 testmysql: [Warning] Using a password on the command line interface can be insecure.Welcome to the MySQL monitor.  Commands end with ; or \g.Your MySQL connection id is 102Server version: 5.7.19-log Source distributionCopyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> DROP TABLE IF EXISTS mycat_sequence;Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> CREATE TABLE mycat_sequence (    -> NAME VARCHAR (50) NOT NULL,    -> current_value INT NOT NULL,    -> increment INT NOT NULL DEFAULT 100,    -> PRIMARY KEY (NAME)    -> ) ENGINE = INNODB ;INSERT INTO mycat_sequence(name,current_value,increment) VALUES ('GLOBAL', 100000, 100);Query OK, 0 rows affected (0.11 sec)mysql> mysql> mysql> mysql> mysql> INSERT INTO mycat_sequence(name,current_value,increment) VALUES ('GLOBAL', 100000, 100);Query OK, 1 row affected (0.00 sec)mysql> mysql> mysql> DROP FUNCTION IF EXISTS `mycat_seq_currval`;Query OK, 0 rows affected (0.00 sec)mysql> DELIMITER ;;mysql> CREATE  FUNCTION `mycat_seq_currval`(seq_name VARCHAR(50))     -> RETURNS varchar(64) CHARSET utf8    ->     DETERMINISTIC    -> BEGIN     ->         DECLARE retval VARCHAR(64);    ->         SET retval="-999999999,null";      ->         SELECT concat(CAST(current_value AS CHAR),",",CAST(increment AS CHAR) ) INTO retval     ->           FROM mycat_sequence  WHERE name = seq_name;      ->         RETURN retval ;     -> END    -> ;;Query OK, 0 rows affected (0.00 sec)mysql> DELIMITER ;mysql> mysql> mysql> DROP FUNCTION IF EXISTS `mycat_seq_nextval`;DELIMITER ;;Query OK, 0 rows affected (0.00 sec)mysql> DELIMITER ;;mysql> CREATE FUNCTION `mycat_seq_nextval`(seq_name VARCHAR(50)) RETURNS varchar(64)    ->  CHARSET utf8    ->     DETERMINISTIC    -> BEGIN     ->          UPDATE mycat_sequence      ->                  SET current_value = current_value + increment     ->                   WHERE name = seq_name;      ->          RETURN mycat_seq_currval(seq_name);      -> END    -> ;;Query OK, 0 rows affected (0.00 sec)mysql> DELIMITER ;mysql> mysql> mysql> mysql> mysql> DROP FUNCTION IF EXISTS `mycat_seq_setval`;Query OK, 0 rows affected (0.00 sec)mysql> DELIMITER ;;mysql> CREATE FUNCTION `mycat_seq_setval`(seq_name VARCHAR(50), value INTEGER)     -> RETURNS varchar(64) CHARSET utf8    ->     DETERMINISTIC    -> BEGIN     ->          UPDATE mycat_sequence      ->                    SET current_value = value      ->                    WHERE name = seq_name;      ->          RETURN mycat_seq_currval(seq_name);      -> END    -> ;;Query OK, 0 rows affected (0.00 sec)mysql> DELIMITER ;mysql>

以下步骤非常关键，让id_db表也支持数据库序列号。

mysql> INSERT INTO mycat_sequence ('ID_DB', 1, 100);mysql> select * from mycat_sequence;+--------+---------------+-----------+| NAME   | current_value | increment |+--------+---------------+-----------+| GLOBAL |        100200 |       100 || ID_DB  |           301 |       100 |+--------+---------------+-----------+2 rows in set (0.00 sec)

vim conf/schema.xml

                        
                
                                                select 1

注意
将mycat_sequence表也放出来，且注意大小写（数据库默认区分大小写）

实验验证：

[root@testA mycat]# mysql -uroot -p123456 -P8066 -h227.0.0.1 testmysql: [Warning] Using a password on the command line interface can be insecure.Welcome to the MySQL monitor.  Commands end with ; or \g.Your MySQL connection id is 2Server version: 5.6.29-mycat-1.6-RELEASE-20161028204710 MyCat Server (OpenCloundDB)Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> show databases;+----------+| DATABASE |+----------+| test     |+----------+1 row in set (0.00 sec)mysql> show tables;+----------------+| Tables in test |+----------------+| id_db          || mycat_sequence |+----------------+2 rows in set (0.00 sec)mysql> drop id_db;ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'id_db' at line 1mysql> drop table id_db;Query OK, 0 rows affected (0.08 sec)mysql> CREATE TABLE `id_db` (`id` int NOT NULL ,`nm` varchar(60) NULL ,PRIMARY KEY (`id`));Query OK, 0 rows affected (0.02 sec)mysql> insert into id_db(id,nm) values(next value for MYCATSEQ_GLOBAL,'id_db');Query OK, 1 row affected (0.10 sec)mysql> insert into id_db(nm) values('db');Query OK, 1 row affected (0.00 sec)mysql> select next value for MYCATSEQ_GLOBAL;+--------+| 100201 |+--------+| 100201 |+--------+1 row in set (0.00 sec)mysql> select * from id_db;+--------+-------+| id     | nm    |+--------+-------+|    303 | db    || 100200 | id_db |+--------+-------+2 rows in set (0.00 sec)mysql> insert into id_db(nm) values('db');Query OK, 1 row affected (0.01 sec)mysql> select * from id_db;+--------+-------+| id     | nm    |+--------+-------+|    303 | db    ||    304 | db    || 100200 | id_db |+--------+-------+3 rows in set (0.00 sec)mysql>

优点：重新部署mycat不受影响
缺点：当配置节点的部署是主从复制，当主挂了切从后会有重复。

注意
节点如果是主从切换后，数据id可能会有异常（重复）

2.4 zookeeper方式

vim conf/server.xml

vim conf/sequence_distributed_conf.properties

INSTANCEID=01CLUSTERID=01

schema的table 增加属性 autoIncrement="true"和 primaryKey="id"

基于ZK 与本地配置的分布式ID 生成器(可以通过ZK 获取集群（机房）唯一InstanceID，也可以通过配置文件配置InstanceID)ID 结构：long 64 位，ID 最大可占63 位
current time millis(微秒时间戳38 位,可以使用17 年)
instanceId（实例ID，可以通过ZK 或者配置文件获取，5 位，也就是十进制0-31）
threadId（线程ID，9 位）
increment(自增,6 位)
一共63 位，可以承受单机房单机器单线程1000*(2^6)=640000 的并发。

优点：无悲观锁，无强竞争，吞吐量更高
缺点：对zookeeper集群的要求增加。

参考资料：
[1] http://mycat.io/
[2] 《分布式数据库架构及企业实践--基于Mycat中间件》
[3] 龙哥官方课程课件、博客

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