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
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
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.go
是 gorm
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.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。
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()
}
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。
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.go
内 dsn
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.go
内 dsn
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。