【架构实战】NewSQL数据库对比（TiDB/CockroachDB）

一、NewSQL简介

NewSQL是新一代分布式关系型数据库，结合了SQL的便利性和NoSQL的可扩展性：

解决的问题：

• 传统关系型数据库无法水平扩展
• NoSQL不支持完整的SQL和事务
• 需要强一致性但又要高可扩展性

代表产品：

• TiDB（PingCAP）
• CockroachDB（CockroachLabs）
• OceanBase（蚂蚁金服）
• YugabyteDB

二、TiDB实战

1. 架构设计

TiDB Server（SQL层，无状态）连接 TiKV 集群（TiKV 1/2/3，每个TiKV管理多个Region），PD Server负责调度。

核心组件：

• TiDB Server：SQL解析和执行，无状态
• TiKV：分布式KV存储引擎（RocksDB）
• PD：集群调度器

2. Docker部署

version: '3'
services:
  pd:
    image: pingcap/pd:latest
    container_name: pd
    ports:
      - "2379:2379"
    volumes:
      - ./pd-data:/pd-data
    command: --name=pd --client-urls=http://0.0.0.0:2379
             --advertise-client-urls=http://pd:2379
             --initial-cluster=pd=http://pd:2380

  tikv1:
    image: pingcap/tikv:latest
    container_name: tikv1
    ports:
      - "20160:20160"
    volumes:
      - ./tikv1-data:/tikv-data
    depends_on:
      - pd
    command: --addr=0.0.0.0:20160 --advertise-addr=tikv1:20160
             --pd=pd:2379 --data-dir=/tikv-data

  tikv2:
    image: pingcap/tikv:latest
    container_name: tikv2
    ports:
      - "20161:20160"
    volumes:
      - ./tikv2-data:/tikv-data
    depends_on:
      - pd
    command: --addr=0.0.0.0:20160 --advertise-addr=tikv2:20160
             --pd=pd:2379 --data-dir=/tikv-data

  tidb:
    image: pingcap/tidb:latest
    container_name: tidb
    ports:
      - "4000:4000"
    depends_on:
      - pd
      - tikv1
      - tikv2
    command: --store=tikv --path=pd:2379

3. MySQL兼容

TiDB完全兼容MySQL协议：

CREATE TABLE orders (
    id BIGINT AUTO_INCREMENT PRIMARY KEY,
    order_no VARCHAR(32) NOT NULL,
    user_id BIGINT NOT NULL,
    shop_id BIGINT NOT NULL,
    order_amount DECIMAL(12,2) NOT NULL,
    order_status TINYINT DEFAULT 1,
    create_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    INDEX idx_user_id (user_id),
    INDEX idx_shop_id (shop_id),
    INDEX idx_order_no (order_no)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

BEGIN;
INSERT INTO orders (order_no, user_id, shop_id, order_amount) 
VALUES ('ORDER001', 1001, 2001, 99.99);
UPDATE inventory SET stock = stock - 1 WHERE product_id = 3001;
COMMIT;

BEGIN PESSIMISTIC;
SELECT * FROM orders WHERE id = 1 FOR UPDATE;
UPDATE orders SET order_status = 2 WHERE id = 1;
COMMIT;

4. Java客户端

@Configuration
public class TiDBConfig {
    
    @Bean
    public DataSource dataSource() {
        HikariConfig config = new HikariConfig();
        config.setJdbcUrl("jdbc:mysql://localhost:4000/order_db");
        config.setUsername("root");
        config.setPassword("");
        config.setMaximumPoolSize(50);
        config.setMinimumIdle(10);
        config.setConnectionTimeout(30000);
        return new HikariDataSource(config);
    }
}

@Service
public class OrderService {
    
    @Autowired
    private DataSource dataSource;
    
    @Transactional
    public void createOrder(OrderRequest request) {
        try (Connection conn = dataSource.getConnection();
             PreparedStatement ps = conn.prepareStatement(
                 "INSERT INTO orders (order_no, user_id, shop_id, order_amount) VALUES (?, ?, ?, ?)")) {
            
            ps.setString(1, request.getOrderNo());
            ps.setLong(2, request.getUserId());
            ps.setLong(3, request.getShopId());
            ps.setBigDecimal(4, request.getAmount());
            
            ps.executeUpdate();
        }
    }
}

5. HTAP能力

TiDB同时支持OLTP和OLAP：

ALTER TABLE orders SET TIFLASH REPLICA 2;

SELECT 
    DATE(create_time) as order_date,
    shop_id,
    COUNT(*) as order_count,
    SUM(order_amount) as total_amount
FROM orders
WHERE create_time >= '2024-01-01'
GROUP BY DATE(create_time), shop_id
ORDER BY total_amount DESC
LIMIT 10;

三、CockroachDB实战

1. 架构设计

Gateway Node（请求路由，无状态）连接多个Node节点，每个Node包含Store，默认3副本强一致（Raft协议）。

核心特性：

• 多副本强一致性（Raft协议）
• 自动分片和负载均衡
• 故障自动恢复
• 地理分布支持

2. Docker部署

version: '3'
services:
  cockroach1:
    image: cockroachdb/cockroach:v23.1
    container_name: cockroach1
    ports:
      - "26257:26257"
      - "8080:8080"
    command: start --insecure --join=cockroach1,cockroach2,cockroach3
    volumes:
      - ./cockroach1-data:/cockroach/cockroach-data

  cockroach2:
    image: cockroachdb/cockroach:v23.1
    container_name: cockroach2
    ports:
      - "26258:26257"
    command: start --insecure --join=cockroach1,cockroach2,cockroach3
    volumes:
      - ./cockroach2-data:/cockroach/cockroach-data

  cockroach3:
    image: cockroachdb/cockroach:v23.1
    container_name: cockroach3
    ports:
      - "26259:26257"
    command: start --insecure --join=cockroach1,cockroach2,cockroach3
    volumes:
      - ./cockroach3-data:/cockroach/cockroach-data

3. SQL语法

CREATE DATABASE IF NOT EXISTS order_db;
USE order_db;

CREATE TABLE orders (
    id UUID DEFAULT gen_random_uuid(),
    order_no VARCHAR(32) NOT NULL,
    user_id INT64 NOT NULL,
    shop_id INT64 NOT NULL,
    order_amount DECIMAL(12,2) NOT NULL,
    order_status INT8 DEFAULT 1,
    create_time TIMESTAMP DEFAULT now(),
    PRIMARY KEY (id),
    INDEX idx_user_id (user_id),
    INDEX idx_shop_id (shop_id),
    UNIQUE INDEX idx_order_no (order_no)
);

BEGIN;
INSERT INTO orders (order_no, user_id, shop_id, order_amount) 
VALUES ('ORDER001', 1001, 2001, 99.99);
UPDATE inventory SET stock = stock - 1 WHERE product_id = 3001;
COMMIT;

CREATE CHANGEFEED FOR TABLE orders
  INTO 'kafka://localhost:9092'
  WITH updated, key_in_value;

4. Java客户端

@Configuration
public class CockroachDBConfig {
    
    @Bean
    public DataSource dataSource() {
        PGSimpleDataSource ds = new PGSimpleDataSource();
        ds.setUrl("jdbc:postgresql://localhost:26257/order_db?sslmode=disable");
        ds.setUser("root");
        ds.setPassword("");
        ds.setConnectionOptions("application_name=order_service");
        return ds;
    }
}

@Service
public class OrderService {
    
    @Autowired
    private DataSource dataSource;
    
    public void createOrderWithRetry(OrderRequest request, int maxRetries) {
        int retry = 0;
        while (retry < maxRetries) {
            try (Connection conn = dataSource.getConnection()) {
                conn.setAutoCommit(false);
                insertOrder(conn, request);
                updateInventory(conn, request);
                conn.commit();
                return;
            } catch (SQLTransactionRetryException e) {
                retry++;
                try {
                    Thread.sleep(100 * retry);
                } catch (InterruptedException ie) {
                    Thread.currentThread().interrupt();
                }
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }
        }
        throw new RuntimeException("重试次数耗尽");
    }
}

5. 地理分布

CREATE TABLE orders (
    id UUID DEFAULT gen_random_uuid(),
    order_no VARCHAR(32) NOT NULL,
    user_id INT64 NOT NULL,
    region STRING NOT NULL,
    create_time TIMESTAMP DEFAULT now(),
    PRIMARY KEY (id, region)
) PARTITION BY LIST (region) (
    PARTITION us_east VALUES IN ('NY', 'MA', 'FL'),
    PARTITION us_west VALUES IN ('CA', 'WA', 'OR'),
    PARTITION eu VALUES IN ('UK', 'DE', 'FR'),
    PARTITION asia VALUES IN ('CN', 'JP', 'KR')
);

ALTER TABLE orders SET locality = REGIONAL BY TABLE AS ROW;

四、TiDB vs CockroachDB对比

维度	TiDB	CockroachDB
创始公司	PingCAP	CockroachLabs
底层存储	RocksDB (TiKV)	RocksDB
一致性	强一致	强一致
SQL兼容	MySQL	PostgreSQL
HTAP	支持（TiFlash）	不支持
地理分布	一般	优秀
性能	优秀	较好
生态	丰富	一般
许可证	Apache 2.0	BSL 1.1
社区	活跃	活跃

五、选型建议

选择TiDB的场景：

• MySQL迁移项目
• 需要HTAP能力（同时支持TP和AP）
• 现有MySQL技术栈
• 数据量级TB级

选择CockroachDB的场景：

• PostgreSQL迁移项目
• 需要强地理分布
• 需要全球化部署
• 对许可证敏感

六、迁移方案

从MySQL迁移到TiDB

cat > task.yaml << EOF
name: mysql-to-tidb
task-mode: all

target-database:
  host: tidb-host
  port: 4000
  user: root

mysql-instances:
  - source-id: mysql-source
    block-allow-list: "instance-1"

routes:
  route-1:
    schema-pattern: "order_db"
    target-schema: "order_db"
EOF

dmctl --master-addr=127.0.0.1:8261 start-task task.yaml
dmctl --master-addr=127.0.0.1:8261 query-status

七、总结

NewSQL是分布式关系型数据库的未来：

• TiDB：MySQL兼容 + HTAP能力强
• CockroachDB：PostgreSQL兼容 + 地理分布强
• 强一致：Raft协议保证
• 水平扩展：自动分片和负载均衡

选型建议：

1. MySQL技术栈 → TiDB
2. PostgreSQL技术栈 → CockroachDB
3. 需要分析能力 → TiDB
4. 需要全球化部署 → CockroachDB

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个人观点，仅供参考