- 关于 TiDB
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- SQL 优化流程
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- 教程
- 同城多中心部署
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- 同城两中心部署
- 读取历史数据
- 使用 Stale Read 功能读取历史数据(推荐)
- 使用系统变量
tidb_snapshot
读取历史数据
- 最佳实践
- Placement Rules 使用文档
- Load Base Split 使用文档
- Store Limit 使用文档
- TiDB 工具
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- tiup dm enable
- tiup dm help
- tiup dm import
- tiup dm list
- tiup dm patch
- tiup dm prune
- tiup dm reload
- tiup dm replay
- tiup dm restart
- tiup dm scale-in
- tiup dm scale-out
- tiup dm start
- tiup dm stop
- tiup dm template
- tiup dm upgrade
- TiDB 集群拓扑文件配置
- DM 集群拓扑文件配置
- TiUP 镜像参考指南
- TiUP 组件文档
- PingCAP Clinic 诊断服务 (Technical Preview)
- TiDB Operator
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ADD COLUMN
ADD INDEX
ADMIN
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ADMIN SHOW TELEMETRY
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ALTER INSTANCE
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ALTER TABLE
ALTER TABLE COMPACT
ALTER USER
ANALYZE TABLE
BACKUP
BATCH
BEGIN
CHANGE COLUMN
CHANGE DRAINER
CHANGE PUMP
COMMIT
CREATE [GLOBAL|SESSION] BINDING
CREATE DATABASE
CREATE INDEX
CREATE PLACEMENT POLICY
CREATE ROLE
CREATE SEQUENCE
CREATE TABLE LIKE
CREATE TABLE
CREATE USER
CREATE VIEW
DEALLOCATE
DELETE
DESC
DESCRIBE
DO
DROP [GLOBAL|SESSION] BINDING
DROP COLUMN
DROP DATABASE
DROP INDEX
DROP PLACEMENT POLICY
DROP ROLE
DROP SEQUENCE
DROP STATS
DROP TABLE
DROP USER
DROP VIEW
EXECUTE
EXPLAIN ANALYZE
EXPLAIN
FLASHBACK TABLE
FLUSH PRIVILEGES
FLUSH STATUS
FLUSH TABLES
GRANT <privileges>
GRANT <role>
INSERT
KILL [TIDB]
LOAD DATA
LOAD STATS
MODIFY COLUMN
PREPARE
RECOVER TABLE
RENAME INDEX
RENAME TABLE
REPLACE
RESTORE
REVOKE <privileges>
REVOKE <role>
ROLLBACK
SELECT
SET DEFAULT ROLE
SET [NAMES|CHARACTER SET]
SET PASSWORD
SET ROLE
SET TRANSACTION
SET [GLOBAL|SESSION] <variable>
SHOW [BACKUPS|RESTORES]
SHOW ANALYZE STATUS
SHOW [GLOBAL|SESSION] BINDINGS
SHOW BUILTINS
SHOW CHARACTER SET
SHOW COLLATION
SHOW [FULL] COLUMNS FROM
SHOW CONFIG
SHOW CREATE PLACEMENT POLICY
SHOW CREATE SEQUENCE
SHOW CREATE TABLE
SHOW CREATE USER
SHOW DATABASES
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SHOW ERRORS
SHOW [FULL] FIELDS FROM
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SHOW INDEX [FROM|IN]
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SHOW PLACEMENT FOR
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USE
WITH
- 数据类型
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- 聚簇索引
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mysql
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ANALYZE_STATUS
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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。
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
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 ?"
)
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(推荐),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:
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
:
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。
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
})
}
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
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。
在 Gitpod Playground 中尝试 gorm: 现在就试试
无需手动初始化表。
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 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"
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:
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:
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。
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。