ClickHouse MaterializeMySQL引擎

一、概述

        ClickHouse 20.8.2.3 版本新增加了MaterializeMySQL的database引擎，该database能
映射到MySQL中的某个database ，并自动在ClickHouse中创建对应的ReplacingMergeTree。ClickHouse服务做为MySQL 副本，读取Binlog并执行DDL和DML请求，实现了基于MySQL Binlog机制的业务数据库实时同步功能。MaterializeMySQL同时支持全量和增量同步，在database创建之初会全量同步MySQL中的表和数据，之后则会通过binlog进行增量同步。

二、使用先决条件

2.1 MySQL部分

（1）确保MySQL开启了binlog功能，且格式为ROW

vim /etc/my.cnf

server-id=1 
log-bin=mysql-bin
binlog_format=ROW

（2）开启GTID部分

gtid_mode=on
enforce_gtid_consistency=1

如果不开启GTID会报错：

Code: 1002. DB::Exception: Received from localhost:9000. DB::Exception: The replication sender thread cannot start in AUTO_POSITION mode: this server has GTID_MODE = OFF instead of ON.. (UNKNOWN_EXCEPTION)

执行上面的操作后需要重启mysql

systemctl restart mysqld

2.2 clickhouse部分

 编辑user.xml文件并重启clickhouse

vim /etc/clickhouse-server/user.xml

<allow_experimental_database_materialized_mysql>1</allow_experimental_database_materialized_mysql>

 要不然会报错如下：

Code: 336. DB::Exception: Received from localhost:9000. DB::Exception: MaterializedMySQL is an experimental database engine. Enable allow_experimental_database_materialized_mysql to use it.. (UNKNOWN_DATABASE_ENGINE)

 三、测试部分

3.1 在MySQL中创建数据表并写入数据

CREATE DATABASE ggl_test;
CREATE TABLE `ggl_test`.`t_organization` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `code` int NOT NULL,
 `name` text DEFAULT NULL,
 `updatetime` datetime DEFAULT NULL,
 PRIMARY KEY (`id`),
 UNIQUE KEY (`code`)
) ENGINE=InnoDB;
INSERT INTO ggl_test.t_organization (code, name,updatetime) 
VALUES(1000,'Realinsight',NOW());
INSERT INTO ggl_test.t_organization (code, name,updatetime) 
VALUES(1001, 'Realindex',NOW());
INSERT INTO ggl_test.t_organization (code, name,updatetime) 
VALUES(1002,'EDT',NOW());


CREATE TABLE `ggl_test`.`t_user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
 `code` int,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB;

INSERT INTO ggl_test.t_user (code) VALUES(1);
INSERT INTO ggl_test.t_user (code) VALUES(2);

3.2 ClickHouse中创建MaterializeMySQL数据库

CREATE DATABASE test_binlog ENGINE = MaterializeMySQL('ggl203:3306','ggl_test','root','123456');

 3.3 查询测试