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Before learning, first understand the concept of sub database and sub table ：https://spiritmark.blog.csdn.net/article/details/109524713

One 、ShardingSphere brief introduction

In database design, consider vertical database and vertical table . As the amount of data in the database increases , Don't immediately think about horizontal segmentation , First consider cache processing , Read / write separation , send By indexing and so on , If these methods can't solve the problem at all , Then consider the horizontal sub database and horizontal sub table .

Problems caused by sub database and sub table ：

• Cross node join query problem （ Pagination 、 Sort ）
• Multiple data source management issues

Apache ShardingSphere Is a set of open source distributed database middleware solutions composed of the ecosystem , It consists of JDBC、 Proxy and Sidecar（ Planning ） this 3 They are independent of each other , But it can mix deployment and use of product composition . They all provide standardized data fragmentation 、 Distributed transaction and database governance functions , It can be applied to such as Java isomorphism 、 Heterogeneous languages 、 Various application scenarios such as cloud native .

Apache ShardingSphere Positioning as a relational database middleware , Designed to be fully reasonable in distributed fields Using the computing and storage capabilities of relational databases , Instead of implementing a new relational database . It doesn't change through focus , And then grasp the essence of things . Relational databases still have a huge market today , It's the cornerstone of every company's core business , The future is hard to shake , At present, we pay more attention to the increment based on the original , Not subversion .

Two 、Sharding-JDBC

Sharding-JDBC It's lightweight java frame , It's an enhanced version of JDBC drive , Simplify the data related operations after sub database and sub table . Create a new project and add dependencies ：

<parent>
    <groupId>org.springframework.bootgroupId>
    <artifactId>spring-boot-parentartifactId>
    <version>2.2.1.RELEASEversion>
parent>

<dependencies>
    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starterartifactId>
    dependency>
    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-testartifactId>
    dependency>
    <dependency>
        <groupId>com.alibabagroupId>
        <artifactId>druid-spring-boot-starterartifactId>
        <version>1.1.20version>
    dependency>
    <dependency>
        <groupId>mysqlgroupId>
        <artifactId>mysql-connector-javaartifactId>
    dependency>
    <dependency>
        <groupId>org.apache.shardingspheregroupId>
        <artifactId>sharding-jdbc-spring-boot-starterartifactId>
        <version>4.0.0-RC1version>
    dependency>
    <dependency>
        <groupId>com.baomidougroupId>
        <artifactId>mybatis-plus-boot-starterartifactId>
        <version>3.0.5version>
    dependency>
    <dependency>
        <groupId>org.projectlombokgroupId>
        <artifactId>lombokartifactId>
    dependency>
dependencies>

2.1 Sharding-JDBC Realize the level table

① According to the way of horizontal table , Create databases and database tables

Horizontal table rules ： If you add cid It's even numbers that add data course_1, If it is an odd number, add it to course_2

CREATE TABLE `course_1`  (
  `cid` bigint(16) NOT NULL,
  `cname` varchar(255) ,
  `userId` bigint(16),
  `cstatus` varchar(16) ,
  PRIMARY KEY (`cid`)
)

② Write entities and Mapper class

@Data
public class Course {
    private Long cid;
    private String cname;
    private Long userId;
    private String cstatus;
}

@Repository
public interface CourseMapper extends BaseMapper<Course> {

}

③ Detailed configuration file

spring:
  main:

    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:

      names: m1
      m1:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://192.168.182.200:3306/course_db?serverTimezone=GMT%2B8
        username: root
        password: 1234
    sharding:
      tables:
        course:

          actual-data-nodes: m1.course_$->{1..2}

          key-generator:
            column: cid
            type: SNOWFLAKE

          table-strategy:
            inline:
              shardingcolumn: cid
              algorithm-expression: course_$->{cid%2+1}
    props:
      sql:
        show: true

mybatis-plus:
  configuration:
    map-underscore-to-camel-case: false

④ test

@RunWith(SpringRunner.class)
@SpringBootTest
public class ShardingSphereTestApplication {

    @Autowired
    CourseMapper courseMapper;

    @Test
    public void addCourse() {
        for (int i = 1; i  10; i++) {
            Course course = new Course();
            course.setCname("java" + i);
            course.setUserId(100L);
            course.setCstatus("Normal" + i);
            courseMapper.insert(course);
        }
    }

    @Test
    public void queryCourse() {
        QueryWrapper<Course> wrapper = new QueryWrapper<>();
        wrapper.eq("cid",493001315358605313L);
        Course course = courseMapper.selectOne(wrapper);
        System.out.println(course);

    }
}

2.2 Sharding-JDBC Realize the horizontal sub database

① Demand analysis ② Create databases and tables

③ Detailed configuration file

spring:
  main:

    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:

      names: m1,m2
      m1:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://192.168.182.200:3306/course_db_2?serverTimezone=GMT%2B8
        username: root
        password: 1234
      m2:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://192.168.182.200:3306/course_db_3?serverTimezone=GMT%2B8
        username: root
        password: 1234
    sharding:

      tables:
        course:

          actual-data-nodes: m$->{1..2}.course_$->{1..2}

          key-generator:
            column: cid
            type: SNOWFLAKE

          database-strategy:
            inline:
              sharding-column: userId
              algorithm-expression: m$->{userId%2+1}
          table-strategy:
            inline:
              sharding-column: cid
              algorithm-expression: course_$->{cid%2+1}
    props:
      sql:
        show: true

mybatis-plus:
  configuration:
    map-underscore-to-camel-case: false

④ Test code

@RunWith(SpringRunner.class)
@SpringBootTest
public class ShardingSphereTestApplication {

    @Autowired
    CourseMapper courseMapper;

    @Test
    public void addCourse() {
        for (int i = 1; i  20; i++) {
            Course course = new Course();
            course.setCname("java" + i);
            int random = (int) (Math.random() * 10);
            course.setUserId(100L + random);
            course.setCstatus("Normal" + i);
            courseMapper.insert(course);
        }
    }

    @Test
    public void queryCourse() {
        QueryWrapper<Course> wrapper = new QueryWrapper<>();
        wrapper.eq("cid", 493001315358605313L);
        Course course = courseMapper.selectOne(wrapper);
        System.out.println(course);
    }
}

Query the actual corresponding SQL：

2.3 Sharding-JDBC Working with common tables

Public table ：

• A table that stores fixed data , Table data rarely changes , Queries are often associated
• Create a common table with the same structure in each database

① Thought analysis ② Create a common table in the corresponding database t_udict，并创建对应实体和 Mapper``

CREATE TABLE `t_udict`  (
  `dict_id` bigint(16) NOT NULL,
  `ustatus` varchar(16) ,
  `uvalue` varchar(255),
  PRIMARY KEY (`dict_id`)
)

③ Detailed configuration file

spring:
  main:

    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:

      names: m1,m2
      m1:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://192.168.182.200:3306/course_db_2?serverTimezone=GMT%2B8
        username: root
        password: 1234
      m2:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://192.168.182.200:3306/course_db_3?serverTimezone=GMT%2B8
        username: root
        password: 1234
    sharding:

      tables:
        course:

          actual-data-nodes: m$->{1..2}.course_$->{1..2}

          key-generator:
            column: cid
            type: SNOWFLAKE

          database-strategy:
            inline:
              sharding-column: userId
              algorithm-expression: m$->{userId%2+1}
          table-strategy:
            inline:
              sharding-column: cid
              algorithm-expression: course_$->{cid%2+1}
        t_udict:
          key-generator:
            column: dict_id
            type: SNOWFLAKE
      broadcast-tables: t_udict

    props:
      sql:
        show: true

mybatis-plus:
  configuration:
    map-underscore-to-camel-case: false

④ To test

After testing ： Data is inserted into each table in each library , Deleting will also delete all data .

@RunWith(SpringRunner.class)
@SpringBootTest
public class ShardingSphereTestApplication {

    @Autowired
    UdictMapper udictMapper;

    @Test
    public void addUdict() {
        Udict udict = new Udict();
        udict.setUstatus("a");
        udict.setUvalue(" Enabled ");
        udictMapper.insert(udict);
    }

    @Test
    public void deleteUdict() {
        QueryWrapper<Udict> wrapper = new QueryWrapper<>();
        wrapper.eq("dict_id", 493080009351626753L);
        udictMapper.delete(wrapper);
    }
}

2.4 Sharding-JDBC Read and write separation

To ensure the stability of database products , Many databases have dual hot standby function . That is to say , The first database server is the production server that provides the business of adding, deleting and modifying ; The second database server is mainly used for reading operations .

Sharding-JDBC adopt sql Sentence semantic analysis , Realize the separation of reading and writing , No data synchronization , Data synchronization usually automatically synchronizes between database clusters .

Detailed configuration file :

spring:
  main:

    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:

      names: m0,s0
      m0:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://192.168.182.200:3306/course_db?serverTimezone=GMT%2B8
        username: root
        password: 1234
      s0:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://192.168.182.200:3307/course_db?serverTimezone=GMT%2B8
        username: root
        password: 1234

    masterslave:
      master-data-source-name: m0
      slave-data-source-names: s0
    props:
      sql:
        show: true

mybatis-plus:
  configuration:
    map-underscore-to-camel-case: false

After testing ： Add, delete and modify operations will pass master database , meanwhile master The database will synchronize data to slave database ; Check operations are all through slave database .

3、 ... and 、Sharding-Proxy

Sharding-Proxy It is positioned as Transparent database proxy side , Provide the server version that encapsulates the binary protocol of the database , Used to support heterogeneous languages , At present, only MySQL and PostgreSQL edition .

Sharding-Proxy It's a stand-alone application , Need to install Service , Perform sub database and sub table or read / write separation configuration , Startup and use . <br> Sharding-proxy The use of reference ：Sharding-Proxy Basic use of . Search on wechat : Xiao Liu in the whole stack