TiDB 和 Golang 的简单 CRUD 应用程序

本文作者：王琦智

本文档将展示如何使用 TiDB 和 Golang 来构造一个简单的 CRUD 应用程序。

注意：

推荐使用 Golang 1.16 以上版本进行 TiDB 的应用程序的编写。

第 1 步：启动你的 TiDB 集群​

本节将介绍 TiDB 集群的启动方法。

使用 TiDB Cloud 免费集群​

创建免费集群。

使用本地集群​

你可以部署一个本地测试的 TiDB 集群或正式的 TiDB 集群。详细步骤，请参考：

部署本地测试 TiDB 集群

部署正式 TiDB 集群。

使用云原生开发环境​

基于 Git 的预配置的开发环境: 现在就试试

该环境会自动克隆代码，并通过 TiUP 部署测试集群。

第 2 步：获取代码​

git clone https://github.com/pingcap-inc/tidb-example-golang.git

使用 go-sql-driver/mysql

使用 gorm（推荐）

进入目录 sqldriver：

cd sqldriver

目录结构如下所示：

. ├── Makefile ├── dao.go ├── go.mod ├── go.sum ├── sql │   └── dbinit.sql ├── sql.go └── sqldriver.go

其中，dbinit.sql 为数据表初始化语句：

USE test; DROP TABLE IF EXISTS player; CREATE TABLE player ( `id` VARCHAR(36), `coins` INTEGER, `goods` INTEGER, PRIMARY KEY (`id`) );

sqldriver.go 是 sqldriver 这个示例程序的主体。因为 TiDB 与 MySQL 协议兼容，因此，需要初始化一个 MySQL 协议的数据源 db, err := sql.Open("mysql", dsn)，以此连接到 TiDB。并在其后，调用 dao.go 中的一系列方法，用来管理数据对象，进行增删改查等操作。

package main import ( "database/sql" "fmt" _ "github.com/go-sql-driver/mysql" ) func main() { // 1. Configure the example database connection. dsn := "root:@tcp(127.0.0.1:4000)/test?charset=utf8mb4" openDB("mysql", dsn, func(db *sql.DB) { // 2. Run some simple examples. simpleExample(db) // 3. Explore more. tradeExample(db) }) } func simpleExample(db *sql.DB) { // Create a player, who has a coin and a goods. err := createPlayer(db, Player{ID: "test", Coins: 1, Goods: 1}) if err != nil { panic(err) } // Get a player. testPlayer, err := getPlayer(db, "test") if err != nil { panic(err) } fmt.Printf("getPlayer: %+v\n", testPlayer) // Create players with bulk inserts. Insert 1919 players totally, with 114 players per batch. err = bulkInsertPlayers(db, randomPlayers(1919), 114) if err != nil { panic(err) } // Count players amount. playersCount, err := getCount(db) if err != nil { panic(err) } fmt.Printf("countPlayers: %d\n", playersCount) // Print 3 players. threePlayers, err := getPlayerByLimit(db, 3) if err != nil { panic(err) } for index, player := range threePlayers { fmt.Printf("print %d player: %+v\n", index+1, player) } } func tradeExample(db *sql.DB) { // Player 1: id is "1", has only 100 coins. // Player 2: id is "2", has 114514 coins, and 20 goods. player1 := Player{ID: "1", Coins: 100} player2 := Player{ID: "2", Coins: 114514, Goods: 20} // Create two players "by hand", using the INSERT statement on the backend. if err := createPlayer(db, player1); err != nil { panic(err) } if err := createPlayer(db, player2); err != nil { panic(err) } // Player 1 wants to buy 10 goods from player 2. // It will cost 500 coins, but player 1 cannot afford it. fmt.Println("\nbuyGoods:\n => this trade will fail") if err := buyGoods(db, player2.ID, player1.ID, 10, 500); err == nil { panic("there shouldnt be success") } // So player 1 has to reduce the incoming quantity to two. fmt.Println("\nbuyGoods:\n => this trade will success") if err := buyGoods(db, player2.ID, player1.ID, 2, 100); err != nil { panic(err) } } func openDB(driverName, dataSourceName string, runnable func(db *sql.DB)) { db, err := sql.Open(driverName, dataSourceName) if err != nil { panic(err) } defer db.Close() runnable(db) }

随后，封装一个用于适配 TiDB 事务的工具包 util，编写以下代码备用：

package util import ( "context" "database/sql" ) type TiDBSqlTx struct { *sql.Tx conn *sql.Conn pessimistic bool } func TiDBSqlBegin(db *sql.DB, pessimistic bool) (*TiDBSqlTx, error) { ctx := context.Background() conn, err := db.Conn(ctx) if err != nil { return nil, err } if pessimistic { _, err = conn.ExecContext(ctx, "set @@tidb_txn_mode=?", "pessimistic") } else { _, err = conn.ExecContext(ctx, "set @@tidb_txn_mode=?", "optimistic") } if err != nil { return nil, err } tx, err := conn.BeginTx(ctx, nil) if err != nil { return nil, err } return &TiDBSqlTx{ conn: conn, Tx: tx, pessimistic: pessimistic, }, nil } func (tx *TiDBSqlTx) Commit() error { defer tx.conn.Close() return tx.Tx.Commit() } func (tx *TiDBSqlTx) Rollback() error { defer tx.conn.Close() return tx.Tx.Rollback() }

在 dao.go 中定义一系列数据的操作方法，用来对提供数据的写入能力。这也是本例子中和核心部分。

package main import ( "database/sql" "fmt" "math/rand" "strings" "github.com/google/uuid" "github.com/pingcap-inc/tidb-example-golang/util" ) type Player struct { ID string Coins int Goods int } // createPlayer create a player func createPlayer(db *sql.DB, player Player) error { _, err := db.Exec(CreatePlayerSQL, player.ID, player.Coins, player.Goods) return err } // getPlayer get a player func getPlayer(db *sql.DB, id string) (Player, error) { var player Player rows, err := db.Query(GetPlayerSQL, id) if err != nil { return player, err } defer rows.Close() if rows.Next() { err = rows.Scan(&player.ID, &player.Coins, &player.Goods) if err == nil { return player, nil } else { return player, err } } return player, fmt.Errorf("can not found player") } // getPlayerByLimit get players by limit func getPlayerByLimit(db *sql.DB, limit int) ([]Player, error) { var players []Player rows, err := db.Query(GetPlayerByLimitSQL, limit) if err != nil { return players, err } defer rows.Close() for rows.Next() { player := Player{} err = rows.Scan(&player.ID, &player.Coins, &player.Goods) if err == nil { players = append(players, player) } else { return players, err } } return players, nil } // bulk-insert players func bulkInsertPlayers(db *sql.DB, players []Player, batchSize int) error { tx, err := util.TiDBSqlBegin(db, true) if err != nil { return err } stmt, err := tx.Prepare(buildBulkInsertSQL(batchSize)) if err != nil { return err } defer stmt.Close() for len(players) > batchSize { if _, err := stmt.Exec(playerToArgs(players[:batchSize])...); err != nil { tx.Rollback() return err } players = players[batchSize:] } if len(players) != 0 { if _, err := tx.Exec(buildBulkInsertSQL(len(players)), playerToArgs(players)...); err != nil { tx.Rollback() return err } } if err := tx.Commit(); err != nil { tx.Rollback() return err } return nil } func getCount(db *sql.DB) (int, error) { count := 0 rows, err := db.Query(GetCountSQL) if err != nil { return count, err } defer rows.Close() if rows.Next() { if err := rows.Scan(&count); err != nil { return count, err } } return count, nil } func buyGoods(db *sql.DB, sellID, buyID string, amount, price int) error { var sellPlayer, buyPlayer Player tx, err := util.TiDBSqlBegin(db, true) if err != nil { return err } buyExec := func() error { stmt, err := tx.Prepare(GetPlayerWithLockSQL) if err != nil { return err } defer stmt.Close() sellRows, err := stmt.Query(sellID) if err != nil { return err } defer sellRows.Close() if sellRows.Next() { if err := sellRows.Scan(&sellPlayer.ID, &sellPlayer.Coins, &sellPlayer.Goods); err != nil { return err } } sellRows.Close() if sellPlayer.ID != sellID || sellPlayer.Goods < amount { return fmt.Errorf("sell player %s goods not enough", sellID) } buyRows, err := stmt.Query(buyID) if err != nil { return err } defer buyRows.Close() if buyRows.Next() { if err := buyRows.Scan(&buyPlayer.ID, &buyPlayer.Coins, &buyPlayer.Goods); err != nil { return err } } buyRows.Close() if buyPlayer.ID != buyID || buyPlayer.Coins < price { return fmt.Errorf("buy player %s coins not enough", buyID) } updateStmt, err := tx.Prepare(UpdatePlayerSQL) if err != nil { return err } defer updateStmt.Close() if _, err := updateStmt.Exec(-amount, price, sellID); err != nil { return err } if _, err := updateStmt.Exec(amount, -price, buyID); err != nil { return err } return nil } err = buyExec() if err == nil { fmt.Println("\n[buyGoods]:\n trade success") tx.Commit() } else { tx.Rollback() } return err } func playerToArgs(players []Player) []interface{} { var args []interface{} for _, player := range players { args = append(args, player.ID, player.Coins, player.Goods) } return args } func buildBulkInsertSQL(amount int) string { return CreatePlayerSQL + strings.Repeat(",(?,?,?)", amount-1) } func randomPlayers(amount int) []Player { players := make([]Player, amount, amount) for i := 0; i < amount; i++ { players[i] = Player{ ID: uuid.New().String(), Coins: rand.Intn(10000), Goods: rand.Intn(10000), } } return players }

sql.go 中存放了 SQL 语句的常量。

package main const ( CreatePlayerSQL = "INSERT INTO player (id, coins, goods) VALUES (?, ?, ?)" GetPlayerSQL = "SELECT id, coins, goods FROM player WHERE id = ?" GetCountSQL = "SELECT count(*) FROM player" GetPlayerWithLockSQL = GetPlayerSQL + " FOR UPDATE" UpdatePlayerSQL = "UPDATE player set goods = goods + ?, coins = coins + ? WHERE id = ?" GetPlayerByLimitSQL = "SELECT id, coins, goods FROM player LIMIT ?" )

第 3 步：运行代码​

本节将逐步介绍代码的运行方法。

第 3 步第 1 部分：go-sql-driver/mysql 表初始化​

使用 go-sql-driver/mysql

使用 gorm（推荐）

在 Gitpod Playground 中尝试 go-sql-driver/mysql: 现在就试试

使用 go-sql-driver/mysql 时，需手动初始化数据库表，若你本地已经安装了 mysql-client，且使用本地集群，可直接在 sqldriver 目录下运行：

make mysql

或直接执行：

mysql --host 127.0.0.1 --port 4000 -u root<sql/dbinit.sql

若你不使用本地集群，或未安装 mysql-client，请直接登录你的集群，并运行 sql/dbinit.sql 文件内的 SQL 语句。

第 3 步第 2 部分：TiDB Cloud 更改参数​

使用 go-sql-driver/mysql

使用 gorm（推荐）

若你使用非本地默认集群、TiDB Cloud 或其他远程集群，更改 sqldriver.go 内 dsn 参数的值：

dsn := "root:@tcp(127.0.0.1:4000)/test?charset=utf8mb4"

若你设定的密码为 123456，而且从 TiDB Cloud 得到的连接字符串为：

mysql --connect-timeout 15 -u root -h xxx.tidbcloud.com -P 4000 -p

那么此处应将参数更改为：

dsn := "root:123456@tcp(xxx.tidbcloud.com:4000)/test?charset=utf8mb4"

第 3 步第 3 部分：运行​

使用 go-sql-driver/mysql

使用 gorm（推荐）

运行 make all，这是以下三个操作的组合：

创建表 (make mysql)：mysql --host 127.0.0.1 --port 4000 -u root<sql/dbinit.sql

构建二进制 (make build)： go build -o bin/sql-driver-example

运行 (make run)： ./bin/sql-driver-example

你也可以单独运行这三个 make 命令或原生命令。

第 4 步：预期输出​

使用 go-sql-driver/mysql

使用 gorm（推荐）

go-sql-driver/mysql 预期输出