TiDB 和 Golang 的简单 CRUD 应用程序

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:

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

  1. git clone https://github.com/pingcap-inc/tidb-example-golang.git
可以看到,go-sql-driver/mysql 实现的代码略显冗余,需要自己管控错误处理逻辑,手动关闭 *sql.Rows,且不能很好的复用代码。并非最佳实践。 当前开源比较流行的 Golang ORM 为 GORM,此处将以 v1.23.5 版本进行说明。 封装一个用于适配 TiDB 事务的工具包 util,编写以下代码备用: go package util import ( "gorm.io/gorm" ) // TiDBGormBegin start a TiDB and Gorm transaction as a block. If no error is returned, the transaction will be committed. Otherwise, the transaction will be rolled back. func TiDBGormBegin(db *gorm.DB, pessimistic bool, fc func(tx *gorm.DB) error) (err error) { session := db.Session(&gorm.Session{}) if session.Error != nil { return session.Error } if pessimistic { session = session.Exec("set @@tidb_txn_mode=pessimistic") } else { session = session.Exec("set @@tidb_txn_mode=optimistic") } if session.Error != nil { return session.Error } return session.Transaction(fc) } 进入目录 gorm shell cd gorm 目录结构如下所示: . ├── Makefile ├── go.mod ├── go.sum └── gorm.go 其中,gorm.gogorm 这个示例程序的主体。使用 gorm 时,相较于 go-sql-driver/mysql,gorm 屏蔽了创建数据库连接时,不同数据库差异的细节,其还封装了大量的操作,如 AutoMigrate、基本对象的 CRUD 等,极大的简化了代码量。 Player 是数据结构体,为数据库表在程序内的映射。Player 的每个属性都对应着 player 表的一个字段。相较于 go-sql-driver/mysql,gorm 的 Player 数据结构体为了给 gorm 提供更多的信息,加入了形如 `gorm:"primaryKey;type:VARCHAR(36);column:id"` 的注解,用来指示映射关系。 go package main import ( "fmt" "math/rand" "github.com/google/uuid" "github.com/pingcap-inc/tidb-example-golang/util" "gorm.io/driver/mysql" "gorm.io/gorm" "gorm.io/gorm/clause" "gorm.io/gorm/logger" ) type Player struct { ID string `gorm:"primaryKey;type:VARCHAR(36);column:id"` Coins int `gorm:"column:coins"` Goods int `gorm:"column:goods"` } func (*Player) TableName() string { return "player" } func main() { // 1. Configure the example database connection. db := createDB() // AutoMigrate for player table db.AutoMigrate(&Player{}) // 2. Run some simple examples. simpleExample(db) // 3. Explore more. tradeExample(db) } func tradeExample(db *gorm.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. db.Clauses(clause.OnConflict{UpdateAll: true}).Create(player1) db.Clauses(clause.OnConflict{UpdateAll: true}).Create(player2) // 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 shouldn't 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 simpleExample(db *gorm.DB) { // Create a player, who has a coin and a goods.. if err := db.Clauses(clause.OnConflict{UpdateAll: true}). Create(&Player{ID: "test", Coins: 1, Goods: 1}).Error; err != nil { panic(err) } // Get a player. var testPlayer Player db.Find(&testPlayer, "id = ?", "test") fmt.Printf("getPlayer: %+v\n", testPlayer) // Create players with bulk inserts. Insert 1919 players totally, with 114 players per batch. bulkInsertPlayers := make([]Player, 1919, 1919) total, batch := 1919, 114 for i := 0; i < total; i++ { bulkInsertPlayers[i] = Player{ ID: uuid.New().String(), Coins: rand.Intn(10000), Goods: rand.Intn(10000), } } if err := db.Session(&gorm.Session{Logger: db.Logger.LogMode(logger.Error)}). CreateInBatches(bulkInsertPlayers, batch).Error; err != nil { panic(err) } // Count players amount. playersCount := int64(0) db.Model(&Player{}).Count(&playersCount) fmt.Printf("countPlayers: %d\n", playersCount) // Print 3 players. threePlayers := make([]Player, 3, 3) db.Limit(3).Find(&threePlayers) for index, player := range threePlayers { fmt.Printf("print %d player: %+v\n", index+1, player) } } func createDB() *gorm.DB { dsn := "root:@tcp(127.0.0.1:4000)/test?charset=utf8mb4" db, err := gorm.Open(mysql.Open(dsn), &gorm.Config{ Logger: logger.Default.LogMode(logger.Info), }) if err != nil { panic(err) } return db } func buyGoods(db *gorm.DB, sellID, buyID string, amount, price int) error { return util.TiDBGormBegin(db, true, func(tx *gorm.DB) error { var sellPlayer, buyPlayer Player if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}). Find(&sellPlayer, "id = ?", sellID).Error; err != nil { return err } if sellPlayer.ID != sellID || sellPlayer.Goods < amount { return fmt.Errorf("sell player %s goods not enough", sellID) } if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}). Find(&buyPlayer, "id = ?", buyID).Error; err != nil { return err } if buyPlayer.ID != buyID || buyPlayer.Coins < price { return fmt.Errorf("buy player %s coins not enough", buyID) } updateSQL := "UPDATE player set goods = goods + ?, coins = coins + ? WHERE id = ?" if err := tx.Exec(updateSQL, -amount, price, sellID).Error; err != nil { return err } if err := tx.Exec(updateSQL, amount, -price, buyID).Error; err != nil { return err } fmt.Println("\n[buyGoods]:\n 'trade success'") return nil }) }
使用 go-sql-driver/mysql 时,首先进入目录 sqldriver shell 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: sql USE test; DROP TABLE IF EXISTS player; CREATE TABLE player ( `id` VARCHAR(36), `coins` INTEGER, `goods` INTEGER, PRIMARY KEY (`id`) ); sqldriver.gosqldriver 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。 go 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 shouldn't 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: go 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() }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。 go 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。 go 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

> 注意: > > 在 Gitpod Playground 中尝试 GORM: 现在就试试 无需手动初始化表。
> 注意: > > 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: shell make mysql 或直接执行: shell 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

若你使用非本地默认集群、TiDB Cloud 或其他远程集群,更改 gorm.godsn 参数值: go 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: go dsn := "root:123456@tcp(xxx.tidbcloud.com:4000)/test?charset=utf8mb4"
若你使用非本地默认集群、TiDB Cloud 或其他远程集群,更改 sqldriver.godsn 参数的值: go 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 tidb.e049234d.d40d1f8b.us-east-1.prod.aws.tidbcloud.com -P 4000 -p 那么此处应将参数更改为: go dsn := "root:123456@tcp(xxx.tidbcloud.com:4000)/test?charset=utf8mb4"

第 3 步第 3 部分:运行

运行 make all,这是以下两个操作的组合: - 构建二进制 (make build):go build -o bin/gorm-example - 运行 (make run):./bin/gorm-example 你也可以单独运行这两个 make 命令或原生命令。
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