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
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
- 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 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：
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）