1. sharding sphere 4.0.0-RC1版本 按年分表实战

1.1. 需求

需要对日志表进行按时间划分表，由于用于后台系统，日志量预估不会太大，因此按年划分表

经过我不断的查阅sharding sphere资料和实践，我最后还是决定先建表，再把actual-data-nodes表结点给定下来，为什么这么说？

我纠结的是到底要不要动态创建表，若想要不自己手动每隔几年维护表，我们当然希望能自动创建。但经过我的实践，sharding sphere本身没有提供该功能，但可以通过分片算法实现类中自定义实现，但前提是我们要随时知道要分片表有几个分片，比如log_2019,log_2020,log_2021，只要我能初始化的时候知道分片有几个表以及表名，那么我就不会查询到不存在的表导致报错，反之则容易报错

我们知道mysql可以通过查询information_schema.TABLES来查询存在的表，但是不知道是不是sharding sphere的bug，我用库名加表名查该库它会强制给我改写成我默认的连接库，导致表不存在，根本查不到

所以我退而求其次，下面我列出我的方案，方案采用的版本是4.0.0-RC1

1.2. 引入pom

1. 先把pom列出来，只给代码不给pom都是耍流氓

         <!-- 分库分表 -->
        <dependency>
            <groupId>org.apache.shardingsphere</groupId>
            <artifactId>sharding-jdbc-spring-boot-starter</artifactId>
            <version>4.0.0-RC1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.shardingsphere</groupId>
            <artifactId>sharding-jdbc-spring-namespace</artifactId>
            <version>4.0.0-RC1</version>
        </dependency>

1.3. application.yml配置

1. 如下配置，分表最重要的是table-strategy分表策略，sharding-column表示分表字段，当插入查询需要指定哪个分表时，必须带上这个条件，否则可能出错，actual-data-nodes表示你分了哪些表，它有一定语法，如下$->{0..1}表示system_log_2020,system_log_2021两张表，我需要在mysql建好这两张表

spring:
  shardingsphere:
    props:
      sql:
        show: true
    datasource:
      names: ds0
      ds0:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://xxxxx:3306/test?useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT%2B8&allowMultiQueries=true
        username: xxx
        password: xxx
    sharding:
      tables:
        system_log:
          actual-data-nodes: ds0.system_log_202$->{0..1}
          table-strategy:
            standard:
              sharding-column: created
              precise-algorithm-class-name: com.xxx.platform.system.log.LogShardingAlgorithm
              range-algorithm-class-name: com.xxx.platform.system.log.LogShardingAlgorithm

1.4. 分表策略

1. 最重要的就是LogShardingAlgorithm这个类

import com.google.common.collect.Range;
import lombok.extern.slf4j.Slf4j;
import org.apache.shardingsphere.api.sharding.standard.PreciseShardingAlgorithm;
import org.apache.shardingsphere.api.sharding.standard.PreciseShardingValue;
import org.apache.shardingsphere.api.sharding.standard.RangeShardingAlgorithm;
import org.apache.shardingsphere.api.sharding.standard.RangeShardingValue;

import java.util.ArrayList;
import java.util.Collection;

/**
 * @author: laoliangliang
 * @description: 日志分片
 * @create: 2020/1/2 10:19
 **/
@Slf4j
public class LogShardingAlgorithm implements PreciseShardingAlgorithm, RangeShardingAlgorithm<Integer> {

    @Override
    public String doSharding(Collection availableTargetNames, PreciseShardingValue shardingValue) {
        String target = shardingValue.getValue().toString();
        return shardingValue.getLogicTableName() + "_" + target.substring(target.lastIndexOf("_") + 1, target.lastIndexOf("_") + 5);
    }

    @Override
    public Collection<String> doSharding(Collection<String> availableTargetNames, RangeShardingValue<Integer> shardingValue) {
        Collection<String> availables = new ArrayList<>();
        Range valueRange = shardingValue.getValueRange();
        for (String target : availableTargetNames) {
            Integer shardValue = Integer.parseInt(target.substring(target.lastIndexOf("_") + 1, target.lastIndexOf("_") + 5));
            if (valueRange.hasLowerBound()) {
                String lowerStr = valueRange.lowerEndpoint().toString();
                Integer start = Integer.parseInt(lowerStr.substring(0, 4));
                if (start - shardValue > 0) {
                    continue;
                }
            }
            if (valueRange.hasUpperBound()) {
                String upperStr = valueRange.upperEndpoint().toString();
                Integer end = Integer.parseInt(upperStr.substring(0, 4));
                if (end - shardValue < 0) {
                    continue;
                }
            }
            availables.add(target);
        }
        return availables;
    }
}

1. 我实现了PreciseShardingAlgorithm, RangeShardingAlgorithm这两个接口，分别表示当created条件为=和between时会分别进入这两个方法，用来判断sql语句命中哪个表
2. 这里要注意，created的><大于小于判断是不起效果的，求范围只能用between，如果我说错了请提醒哦
3. 接下来调用sql语句我是这样写的

SELECT created,user_name,`action`,id FROM system_log
<where>
    <if test="id!=null and id!=''">
        and pk_id=#{id}
    </if>
    <if test="startTime != null and endTime != null">
        and created BETWEEN #{startTime} and #{endTime}
    </if>
</where>
order by created desc

1.5. 结果

1. mybatis插入后日志如下，可以看到mybatis打印的日志表名还是system_log，但实际对应数据库有system_log_2020,system_log_2021两张表，我插入的时间是2020年，所以只插入2020的表

2020-01-07 16:40:28.165 DEBUG 7780 --- [pool-4-thread-1] c.o.p.p.m.S.insertSelective              : ==>  Preparing: INSERT INTO system_log ( type,pk_id,remark,user_name,created,action ) VALUES( ?,?,?,?,?,? ) 
2020-01-07 16:40:28.165 DEBUG 7780 --- [pool-4-thread-1] c.o.p.p.m.S.insertSelective              : ==> Parameters: 1(Integer), 0(Integer), string(String), 15162191629(String), 2020-01-07 16:40:28.161(Timestamp), 内容(String)
2020-01-07 16:40:28.198  INFO 7780 --- [pool-4-thread-1] ShardingSphere-SQL                       : Rule Type: sharding
2020-01-07 16:40:28.198  INFO 7780 --- [pool-4-thread-1] ShardingSphere-SQL                       : Logic SQL: INSERT INTO system_log  ( type,pk_id,remark,user_name,created,action ) VALUES( ?,?,?,?,?,? )
2020-01-07 16:40:28.198  INFO 7780 --- [pool-4-thread-1] ShardingSphere-SQL                       : SQLStatement: InsertStatement(super=DMLStatement(super=AbstractSQLStatement(type=DML, tables=Tables(tables=[Table(name=system_log, alias=Optional.absent())]), routeConditions=Conditions(orCondition=OrCondition(andConditions=[AndCondition(conditions=[Condition(column=Column(name=created, tableName=system_log), operator=EQUAL, compareOperator=null, positionValueMap={}, positionIndexMap={0=4})])])), encryptConditions=Conditions(orCondition=OrCondition(andConditions=[])), sqlTokens=[TableToken(tableName=system_log, quoteCharacter=NONE, schemaNameLength=0), SQLToken(startIndex=24)], parametersIndex=6, logicSQL=INSERT INTO system_log  ( type,pk_id,remark,user_name,created,action ) VALUES( ?,?,?,?,?,? )), deleteStatement=false, updateTableAlias={}, updateColumnValues={}, whereStartIndex=0, whereStopIndex=0, whereParameterStartIndex=0, whereParameterEndIndex=0), columnNames=[type, pk_id, remark, user_name, created, action], values=[InsertValue(columnValues=[org.apache.shardingsphere.core.parse.old.parser.expression.SQLPlaceholderExpression@21625d01, org.apache.shardingsphere.core.parse.old.parser.expression.SQLPlaceholderExpression@34dda176, org.apache.shardingsphere.core.parse.old.parser.expression.SQLPlaceholderExpression@5d631384, org.apache.shardingsphere.core.parse.old.parser.expression.SQLPlaceholderExpression@13cfbf64, org.apache.shardingsphere.core.parse.old.parser.expression.SQLPlaceholderExpression@20f67249, org.apache.shardingsphere.core.parse.old.parser.expression.SQLPlaceholderExpression@79f9b130])])
2020-01-07 16:40:28.198  INFO 7780 --- [pool-4-thread-1] ShardingSphere-SQL                       : Actual SQL: ds0 ::: INSERT INTO system_log_2020   (type, pk_id, remark, user_name, created, action) VALUES (?, ?, ?, ?, ?, ?) ::: [1, 0, string, 15162191629, 2020-01-07 16:40:28.161, 内容]
2020-01-07 16:40:28.210 DEBUG 7780 --- [pool-4-thread-1] c.o.p.p.m.S.insertSelective              : <==    Updates: 1

1. 如上的查询语句结果也同理，只查2020年

查询参数

{
  "endTime": "2020-01-10 01:01:01",
  "id": 435,
  "page": 1,
  "pageSize": 10,
  "startTime": "2020-01-01 01:01:01"
}

查询结果

2020-01-07 16:50:49.878 DEBUG 5408 --- [nio-9000-exec-2] c.o.p.p.m.S.getReportLogList             : ==>  Preparing: SELECT created,user_name,`action`,id,remark FROM system_log WHERE pk_id=? and created BETWEEN ? and ? order by created desc LIMIT ? 
2020-01-07 16:50:49.879 DEBUG 5408 --- [nio-9000-exec-2] c.o.p.p.m.S.getReportLogList             : ==> Parameters: 435(Integer), 2020-01-01 01:01:01.0(Timestamp), 2020-01-10 01:01:01.0(Timestamp), 10(Integer)
2020-01-07 16:50:49.891  INFO 5408 --- [nio-9000-exec-2] ShardingSphere-SQL                       : Rule Type: sharding
2020-01-07 16:50:49.891  INFO 5408 --- [nio-9000-exec-2] ShardingSphere-SQL                       : Logic SQL: SELECT created,user_name,`action`,id,remark FROM system_log
         WHERE  pk_id=?
            
            
                and created BETWEEN ? and ? 
        order by created desc LIMIT ? 
2020-01-07 16:50:49.891  INFO 5408 --- [nio-9000-exec-2] ShardingSphere-SQL                       : SQLStatement: SelectStatement(super=DQLStatement(super=AbstractSQLStatement(type=DQL, tables=Tables(tables=[Table(name=system_log, alias=Optional.absent())]), routeConditions=Conditions(orCondition=OrCondition(andConditions=[AndCondition(conditions=[Condition(column=Column(name=created, tableName=system_log), operator=BETWEEN, compareOperator=null, positionValueMap={}, positionIndexMap={0=1, 1=2})])])), encryptConditions=Conditions(orCondition=OrCondition(andConditions=[])), sqlTokens=[TableToken(tableName=system_log, quoteCharacter=NONE, schemaNameLength=0)], parametersIndex=4, logicSQL=SELECT created,user_name,`action`,id,remark FROM system_log
         WHERE  pk_id=?
            
            
                and created BETWEEN ? and ? 
        order by created desc LIMIT ? )), containStar=false, firstSelectItemStartIndex=7, selectListStopIndex=42, groupByLastIndex=0, items=[CommonSelectItem(expression=created, alias=Optional.absent()), CommonSelectItem(expression=user_name, alias=Optional.absent()), CommonSelectItem(expression=action, alias=Optional.absent()), CommonSelectItem(expression=id, alias=Optional.absent()), CommonSelectItem(expression=remark, alias=Optional.absent())], groupByItems=[], orderByItems=[OrderItem(owner=Optional.absent(), name=Optional.of(created), orderDirection=DESC, nullOrderDirection=ASC, index=-1, expression=null, alias=Optional.absent())], limit=Limit(offset=null, rowCount=LimitValue(value=-1, index=3, boundOpened=false)), subqueryStatement=null, subqueryStatements=[], subqueryConditions=[])
2020-01-07 16:50:49.891  INFO 5408 --- [nio-9000-exec-2] ShardingSphere-SQL                       : Actual SQL: ds0 ::: SELECT created,user_name,`action`,id,remark FROM system_log_2020
         WHERE  pk_id=?
            
            
                and created BETWEEN ? and ? 
        order by created desc LIMIT ?  ::: [435, 2020-01-01 01:01:01.0, 2020-01-10 01:01:01.0, 10]
2020-01-07 16:50:49.898 DEBUG 5408 --- [nio-9000-exec-2] c.o.p.p.m.S.getReportLogList             : <==      Total: 2

1.6. 总结

这次主要的碰壁内容就是created的大于小于问题，大于小于触发不了表分片行为，需要特别注意。希望对你有帮助

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