Spring Boot分表查询动态映射实战

问题背景

在Spring Boot与MyBatis整合的项目中，数据分表（如按时间、ID哈希等规则拆分）是常见的优化策略。但分表后，前端传递的查询条件需动态映射到对应子表，这对查询逻辑的实现提出了挑战。

动态表名映射方案

方案一：MyBatis拦截器动态改写SQL

通过自定义MyBatis拦截器（Interceptor），在SQL执行前动态替换表名。例如，根据用户ID的哈希值路由到user_0或user_1表：

@Intercepts({@Signature(type= StatementHandler.class, method="prepare", args={Connection.class, Integer.class})})
public class TableShardInterceptor implements Interceptor {
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        BoundSql boundSql = ((StatementHandler) invocation.getTarget()).getBoundSql();
        String sql = boundSql.getSql();
        if (sql.contains("{shard_key}")) { // 标记需替换的表名
            Object param = boundSql.getParameterObject();
            int shardValue = ((UserQuery) param).getUserId() % 2; // 分表逻辑
            sql = sql.replace("{shard_key}", "user_" + shardValue);
        }
        return invocation.proceed();
    }
}

Mapper XML配置：

<select id="selectByUser" resultType="User">
    SELECT * FROM {shard_key} WHERE user_id = #{userId}
</select>

方案二：Spring AOP + 注解路由

通过自定义注解标记分表逻辑，利用AOP在Service层动态选择数据源或表名：

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface TableShard {
    String key(); // 如 "userId"
    String prefix(); // 如 "user_"
}

@Aspect
@Component
public class TableShardAspect {
    @Around("@annotation(shard)")
    public Object routeTable(ProceedingJoinPoint joinPoint, TableShard shard) throws Throwable {
        Object[] args = joinPoint.getArgs();
        int shardValue = (int) args[0] % 2; // 假设第一个参数是userId
        String tableName = shard.prefix() + shardValue;
        // 将tableName传递到Mapper（可通过ThreadLocal或参数包装）
        return joinPoint.proceed();
    }
}

Service层调用示例：

@TableShard(key = "userId", prefix = "user_")
public User getUserById(int userId) {
    return userMapper.selectByUserId(userId);
}

方案三：MyBatis动态SQL拼接

在Mapper XML中使用<script>标签动态拼接表名，适用于简单分表规则：

<select id="selectByOrder" resultType="Order">
    <script>
        SELECT * FROM order_${tableSuffix}
        WHERE order_id = #{orderId}
        <if test="createTime != null">
            AND create_time = #{createTime}
        </if>
    </script>
</select>

参数传递：

public interface OrderMapper {
    List<Order> selectByOrder(@Param("orderId") String orderId, 
                             @Param("tableSuffix") String tableSuffix);
}

前端交互设计建议

透明化分表逻辑：前端无需感知分表规则，只需传递原始参数（如userId、orderId），后端根据规则计算表名。
批量查询兼容性：若需跨多表查询（如时间范围查询），后端应聚合结果后返回，避免前端多次调用。

性能优化注意事项

缓存表路由结果：对高频访问的实体（如用户信息），缓存表名与ID的映射关系。
避免全表扫描：确保分表字段（如user_id）是查询条件的一部分，否则需遍历所有子表。

错误处理

子表不存在时：通过CREATE TABLE IF NOT EXISTS在首次查询时自动建表，或返回明确错误提示。
分片键缺失：校验请求参数，拒绝无分片键的查询。

通过上述方案，可灵活实现分表查询的透明化，保持前端交互简洁的同时，提升后端数据处理能力。

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