Build a Simple CRUD App with TiDB and Golang
This document describes how to use TiDB and Golang to build a simple CRUD application.
Step 1. Launch your TiDB cluster
The following introduces how to start a TiDB cluster.
Use a TiDB Cloud free cluster
For detailed steps, see Create a free cluster.
Use a local cluster
For detailed steps, see Deploy a local test cluster or Deploy a TiDB Cluster Using TiUP.
Step 2. Get the code
git clone https://github.com/pingcap-inc/tidb-example-golang.git
- Using go-sql-driver/mysql
- Using GORM (Recommended)
Change to the sqldriver
directory:
cd sqldriver
The structure of this directory is as follows:
.
├── Makefile
├── dao.go
├── go.mod
├── go.sum
├── sql
│ └── dbinit.sql
├── sql.go
└── sqldriver.go
You can find initialization statements for the table creation in dbinit.sql
:
USE test;
DROP TABLE IF EXISTS player;
CREATE TABLE player (
`id` VARCHAR(36),
`coins` INTEGER,
`goods` INTEGER,
PRIMARY KEY (`id`)
);
sqldriver.go
is the main body of the sqldriver
. TiDB is highly compatible with the MySQL protocol, so you need to initialize a MySQL source instance db, err := sql.Open("mysql", dsn)
to connect to TiDB. Then, you can use dao.go
to read, edit, add, and delete data.
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)
}
To adapt TiDB transactions, write a toolkit util according to the following code:
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
defines a set of data manipulation methods to provide the ability to write data. This is also the core part of this example.
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
defines SQL statements as constants:
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 ?"
)
Compared with GORM, the go-sql-driver/mysql implementation might be not a best practice, because you need to write error handling logic, close *sql.Rows
manually and cannot reuse code easily, which makes your code slightly redundant.
GORM is a popular open-source ORM library for Golang. The following instructions take v1.23.5
as an example.
To adapt TiDB transactions, write a toolkit util according to the following code:
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()
}
Change to the gorm
directory:
cd gorm
The structure of this directory is as follows:
.
├── Makefile
├── go.mod
├── go.sum
└── gorm.go
gorm.go
is the main body of the gorm
. Compared with go-sql-driver/mysql, GORM avoids differences in database creation between different databases. It also implements a lot of operations, such as AutoMigrate and CRUD of objects, which greatly simplifies the code.
Player
is a data entity struct that is a mapping for tables. Each property of a Player
corresponds to a field in the player
table. Compared with go-sql-driver/mysql, Player
in GORM adds struct tags to indicate mapping relationships for more information, such as gorm:"primaryKey;type:VARCHAR(36);column:id"
.
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
})
}
Step 3. Run the code
The following content introduces how to run the code step by step.
Step 3.1 Table initialization
- Using go-sql-driver/mysql
- Using GORM (Recommended)
When using go-sql-driver/mysql, you need to initialize the database tables manually. If you are using a local cluster, and MySQL client has been installed locally, you can run it directly in the sqldriver
directory:
make mysql
Or you can execute the following command:
mysql --host 127.0.0.1 --port 4000 -u root<sql/dbinit.sql
If you are using a non-local cluster or MySQL client has not been installed, connect to your cluster and run the statement in the sql/dbinit.sql
file.
When using go-sql-driver/mysql, you need to connect to your cluster and run the statement in the sql/dbinit.sql
file to initialize the database tables manually.
No need to initialize tables manually.
Step 3.2 Modify parameters for TiDB Cloud
- Using go-sql-driver/mysql
- Using GORM (Recommended)
If you are using a non-local default cluster, such as TiDB Cloud or other remote clusters, modify the value of the dsn
in sqldriver.go
:
dsn := "root:@tcp(127.0.0.1:4000)/test?charset=utf8mb4"
Suppose that the password you set is 123456
and the connection string you get from TiDB Cloud is the following:
mysql --connect-timeout 15 -u root -h xxx.tidbcloud.com -P 4000 -p
In this case, you can modify the parameters as follows:
dsn := "root:123456@tcp(xxx.tidbcloud.com:4000)/test?charset=utf8mb4"
If you are using a non-local default cluster, such as TiDB Cloud or other remote clusters, modify the value of the dsn
in gorm.go
:
dsn := "root:@tcp(127.0.0.1:4000)/test?charset=utf8mb4"
Suppose that the password you set is 123456
and the connection string you get from TiDB Cloud is the following:
mysql --connect-timeout 15 -u root -h xxx.tidbcloud.com -P 4000 -p
In this case, you can modify the parameters as follows:
dsn := "root:123456@tcp(xxx.tidbcloud.com:4000)/test?charset=utf8mb4"
Step 3.3 Run
- Using go-sql-driver/mysql
- Using GORM (Recommended)
To run the code, you can run make mysql
, make build
and make run
respectively:
make mysql # this command executes `mysql --host 127.0.0.1 --port 4000 -u root<sql/dbinit.sql`
make build # this command executes `go build -o bin/sql-driver-example`
make run # this command executes `./bin/sql-driver-example`
Or you can use the native commands:
mysql --host 127.0.0.1 --port 4000 -u root<sql/dbinit.sql
go build -o bin/sql-driver-example
./bin/sql-driver-example
Or run the make all
command directly, which is a combination of make mysql
, make build
and make run
.
To run the code, you can run make build
and make run
respectively:
make build # this command executes `go build -o bin/gorm-example`
make run # this command executes `./bin/gorm-example`
Or you can use the native commands:
go build -o bin/gorm-example
./bin/gorm-example
Or run the make
command directly, which is a combination of make build
and make run
.
Step 4. Expected output
- Using go-sql-driver/mysql
- Using GORM (Recommended)