給小白演示 分庫分表案例
大家好,我是老田,受羣裏小夥伴之邀,搞一個分庫分表案例,這樣讓很多沒用過分庫分表的心裏也有個底,不然永遠看到的都是網上的各種概念和解決方案性的文章。
說明:由於是給小白看的,所以大神勿噴,建議出門左轉去學更牛逼的技術。
需求
由於用戶表過於龐大,採取相關 SQL 優化,還是不能滿足,所以現對其進行做分庫分表。
數據庫:my-sharding
數據庫表:t_user
建表語句如下:
DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user` (
`id` bigint NOT NULL AUTO_INCREMENT,
`user_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`age` int NOT NULL,
`gender` int NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
關於數據庫分庫分表通常有兩種方案:
-
垂直拆分
-
水平拆分
下面我們來演示水平拆分,大致思路:
通過 t_user 表的 id 進行 hash,然後再和數據庫個數進行取模,得出對應數據庫。
通過 hash 值和每個數據庫中表的個數進行取模,得出對應表名。
創建數據庫和表
加入有 2000 萬條數據,那麼爲了方便演示,我們就暫定分爲五個庫,每個數據庫對應五個表。
理想狀態:2000 萬 / 5/4,那麼每個數據庫分得 400 萬,每個表分得 80 萬。
總之,分庫分表後,我們的每一張表的數據庫和表都與之前的確實不是一個量級了。
五個數據庫:
每個數據庫有五張表:
建表語句如下:
DROP TABLE IF EXISTS `t_user_0`;
CREATE TABLE `t_user_0` (
`id` bigint NOT NULL AUTO_INCREMENT,
`user_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`age` int NOT NULL,
`gender` int NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `t_user_1`;
CREATE TABLE `t_user_1` (
`id` bigint NOT NULL AUTO_INCREMENT,
`user_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`age` int NOT NULL,
`gender` int NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `t_user_2`;
CREATE TABLE `t_user_2` (
`id` bigint NOT NULL AUTO_INCREMENT,
`user_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`age` int NOT NULL,
`gender` int NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `t_user_3`;
CREATE TABLE `t_user_3` (
`id` bigint NOT NULL AUTO_INCREMENT,
`user_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`age` int NOT NULL,
`gender` int NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `t_user_4`;
CREATE TABLE `t_user_4` (
`id` bigint NOT NULL AUTO_INCREMENT,
`user_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
`age` int NOT NULL,
`gender` int NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
項目創建
使用技術棧:JDK8
+MySQL
+Spring Boot
+Mybatis
+Shardingsphere
+Druid
maven 相關依賴:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.1.0</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.16</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.2.3</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.shardingsphere</groupId>
<artifactId>sharding-jdbc-spring-boot-starter</artifactId>
<version>4.0.1</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.17</version>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>29.0-jre</version>
</dependency>
配置文件相關配置如下:
server.port=9002
mybatis.mapper-locations=classpath:/mapper/*.xml
# mybatis.type-aliases-package=com.neutral.idmapping.dbshard.pojo
##### 連接池配置 #######
# 過濾器設置(第一個stat很重要,沒有的話會監控不到SQL)
spring.datasource.druid.filters=stat,wall,log4j2
##### WebStatFilter配置 #######
#啓用StatFilter
spring.datasource.druid.web-stat-filter.enabled=true
#添加過濾規則
spring.datasource.druid.web-stat-filter.url-pattern=/*
#排除一些不必要的url
spring.datasource.druid.web-stat-filter.exclusions=*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*
#開啓session統計功能
spring.datasource.druid.web-stat-filter.session-stat-enable=true
#缺省sessionStatMaxCount是1000個
spring.datasource.druid.web-stat-filter.session-stat-max-count=1000
#spring.datasource.druid.web-stat-filter.principal-session-name=
#spring.datasource.druid.web-stat-filter.principal-cookie-name=
#spring.datasource.druid.web-stat-filter.profile-enable=
##### StatViewServlet配置 #######
#啓用內置的監控頁面
spring.datasource.druid.stat-view-servlet.enabled=true
#內置監控頁面的地址
spring.datasource.druid.stat-view-servlet.url-pattern=/druid/*
#關閉 Reset All 功能
spring.datasource.druid.stat-view-servlet.reset-enable=false
#設置登錄用戶名
spring.datasource.druid.stat-view-servlet.login-username=admin
#設置登錄密碼
spring.datasource.druid.stat-view-servlet.login-password=admin
spring.shardingsphere.props.sql.show=false
#數據庫名
spring.shardingsphere.datasource.names=dp0,dp1,dp2,dp3,dp4
#datasource
spring.shardingsphere.datasource.dp0.type=com.alibaba.druid.pool.DruidDataSource
spring.shardingsphere.datasource.dp0.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.dp0.url=jdbc:mysql://localhost:3306/my-sharding_0?useUnicode=true&characterEncoding=utf-8&serverTimeZone=CTT&allowPublicKeyRetrieval=true&serverTimezone=UTC
spring.shardingsphere.datasource.dp0.username=root
spring.shardingsphere.datasource.dp0.password=123456
----------相同的代碼部分這裏就不貼了-------
# 對應 dp1、dp2、dp3、dp4 和上面dp0配置類似,不一樣的就是數據庫名字不一樣
# 因爲我使用的本地創建多個數據庫演示的,這裏就沒有必要重複累贅了
#actual-data-nodes
#這裏是配置所有的 庫.表 的集合
#比如我這裏配置的意思是 dp0.data_0 , dp0.data_1 ,dp0.data_2 , ...
#此縮寫方式使用了shardingsphere 官方推薦的語法
#t_user 邏輯表名 在UserMapper.xml中使用
spring.shardingsphere.sharding.tables.t_user.actual-data-nodes=dp$->{0..4}.t_user_$->{0..4}
#table
#設置了以data中字段id作爲分表的標準,這樣到時候就會將id作爲參數傳入到下面配置的我們自定義的分表方法中做具體操
spring.shardingsphere.sharding.tables.t_user.table-strategy.standard.sharding-column=id
spring.shardingsphere.sharding.tables.t_user.table-strategy.standard.precise-algorithm-class-name=com.tian.shardingdemo.common.TableShardingAlgorithm
#database
#設置了以data中字段id作爲分庫的標準,這樣到時候就會將id作爲參數傳入到下面配置的我們自定義的分庫方法中做具體操作
spring.shardingsphere.sharding.tables.t_user.database-strategy.standard.sharding-column=id
spring.shardingsphere.sharding.tables.t_user.database-strategy.standard.precise-algorithm-class-name=com.tian.shardingdemo.common.DbShardingAlgorithm
分庫分表的兩個分片類:
/**
* 分庫
*/
public class DbShardingAlgorithm implements PreciseShardingAlgorithm<Long> {
private Logger logger = LoggerFactory.getLogger(DbShardingAlgorithm.class);
@Override
public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Long> shardingValue) {
String databaseName = availableTargetNames.stream().findFirst().get();
for (String dbName : availableTargetNames) {
//shardingValue.getValue()就是配置的傳入的值
//我們這裏選用的是傳入sql中的id字段的值
String targetDb + genderToTableSuffix(shardingValue.getValue());
if (dbName.equals(targetDbName)) {
//匹配到對應的數據庫,比如 dp0
//這個數據庫名對應數據源處配置的dp0,dp1,...
logger.info("數據庫名=" + dbName);
databaseName = dbName;
}
}
return databaseName;
}
private String genderToTableSuffix(Long value) {
//將id字段的值去hash值後去模運算得到分庫的數字(就是一種算法而已)
int i = Hashing.murmur3_128(1823977).newHasher().putString(String.valueOf(value), Charsets.UTF_8).hash().asInt();
//hash與表個數進行取模
return String.valueOf(Math.abs(i) % 5);
}
}
/**
* 分表
*/
public class TableShardingAlgorithm implements PreciseShardingAlgorithm<Long> {
private Logger logger = LoggerFactory.getLogger(TableShardingAlgorithm.class);
@Override
public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Long> shardingValue) {
String table = availableTargetNames.stream().findFirst().get();
String targetName = "t_user_" + genderToTableSuffix(shardingValue.getValue());
for (String tableName : availableTargetNames) {
//檢查計算出來的表名是否存在
if (tableName.equals(targetName)) {
logger.info("表名= " + tableName);
table = tableName;
}
}
return table;
}
private String genderToTableSuffix(Long value) {
//算出一個hash值 int類型
int i = Hashing.murmur3_128(8947189).newHasher().putString(String.valueOf(value), Charsets.UTF_8).hash().asInt();
//hash與表個數進行取模
return String.valueOf(Math.abs(i) % 5);
}
}
下面是業務部分代碼,先看UserMapper.xml
內容:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.tian.shardingdemo.mapper.UserMapper">
<resultMap id="User" type="com.tian.shardingdemo.entity.User">
<id column="id" property="id"/>
<result column="user_name" property="userName"/>
</resultMap>
<insert id="insert">
INSERT INTO t_user (id, user_name,age,gender) VALUES ( #{id},#{userName},#{age},#{gender}
);
</insert>
<select id="selectUserById" resultMap="User">
select * from t_user
<where>
<if test="id != null">
id = #{id}
</if>
</where>
</select>
<update id="updateAuthorIfNecessary">
update t_user
<trim prefix="SET" suffixOverrides=",">
<if test="userName != null and userName != ''">
`user_name` = #{userName},
</if>
<if test="gender != null and gender != 0">
gender = #{gender},
</if>
<if test="age != null and age != 0">
age = #{age},
</if>
</trim>
where id=#{id}
</update>
</mapper>
UserMapper
接口:
import com.tian.shardingdemo.entity.User;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Repository;
@Mapper
@Repository
public interface UserMapper {
User selectUserById(@Param("id") Long id);
int updateAuthorIfNecessary(User user);
int insert(User user);
}
爲了更好地演示,我這裏加入了controller
層和service
層,這也是大家平常開發套路。
service
層代碼如下:
public interface IUserService {
User selectUserById(Long id);
void add(Long id);
}
@Service
public class UserServiceImpl implements IUserService {
@Resource
private UserMapper userMapper;
@Override
public User selectUserById(Long id) {
return userMapper.selectUserById(id);
}
@Override
public void add(Long id) {
User user = new User();
user.setAge(22);
user.setGender(1);
user.setId(id);
user.setUserName("tian" + id);
userMapper.insert(user);
}
}
controller 層代碼如下:
@RestController
@RequestMapping
public class UserController {
@Resource
private IUserService userService;
@RequestMapping(value = "/user/{id}", method = RequestMethod.GET)
public User selectUserById(@PathVariable("id") Long id) {
return userService.selectUserById(id);
}
@PostMapping("/add")
public Object add(@RequestBody Map<String,Long> params) {
Long id = params.get("id");
userService.add(id);
return "ok";
}
}
最後是項目的啓動類:
@SpringBootApplication
@MapperScan({"com.tian.shardingdemo.mapper"})
public class ShardingDemoApplication {
public static void main(String[] args) {
SpringApplication.run(ShardingDemoApplication.class, args);
}
}
啓動項目,啓動成功:
下面我們來演示一下新增數據和查詢。
添加數據到數據庫中
先來添加數據到數據庫中,這裏使用的是 IDEA 中 restful 工具:
後臺日誌:
再查看數據庫表中:
到此,我們的數據依舊落庫,下面我們來演示一下數據查詢。
數據查詢
瀏覽器裏輸入:
http://localhost:9002/user/7
返回數據:
{"id":7,"userName":"tian7","age":22,"gender":1}
後臺日誌:
從日誌和返回結果可以看出,已經爲我們正確的選擇到對應的數據庫和表了,這樣,一個分庫分表的查詢就成功了。
總結
本文沒有太多的概念,直接使用案例演示。相關概念性的文章,還有分庫分表解決方案的文章,網上一堆堆的,感興趣可以自行查閱。
參考:http://01vh0.cn/mLQwN
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來源:https://mp.weixin.qq.com/s/rE9YNaF_qJkM93wRZezbdw