golang gorm —— 事务、回滚、savepoint

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gorm事务

model定义

type Roles []stringtype Teacher struct {gorm.ModelName     string   `gorm:"size:256"`Email    string   `gorm:"size:256"`Salary   float64  `gorm:"scale:2;precision:7"`   // 指定小数部分宽度为2，列宽度为7. 列宽：【整数部分+小数部分的总长度】【不含小数点】Age      uint8    `gorm:"check:age>30"`Birthday int64    `gorm:"serializer:unixtime;type:time"`  // 反序列化方式 unixtime， 类型为timeRoles    Roles    `gorm:"serializer:json"`JobInfo  Job      `gorm:"embedded;embeddedPrefix:job_"`   // 嵌套字段， 嵌入字段的列名前缀job_JobInfo2 Job      `gorm:"type:bytes;serializer:gob"`      // 字节流类型，gob反序列化,go自己的序列化方法,跨语言项目的时候，不建议用
}type Job struct {Title    stringLocation string
}type Course struct {gorm.ModelName   string  `gorm:"size:256"`Price  float64 `gorm:"scale:2;precision:7"`UserID uint    `gorm:"type:int"`
}

自动事务

gorm提供了自动事务的机制，不需要我们手动提交和回滚

func Transaction() {t := Teacher{Name:   "yuan",Age:    41,Salary: 122345.123,Email:  "yuan@test.com",}c := Course{Name:  "golang",Price: 12345.1234,}DB.Transaction(func(tx *gorm.DB) error {if err := tx.Create(&t).Error; err != nil {// 返回err 会自动回滚事务return err}c.UserID = t.IDif err := tx.Create(&c).Error; err != nil {return err}// 返回nil 则提交事务return nil})
}

嵌套事务

gorm事务可以嵌套，大事务里嵌套小事务，只有大事务成功提交，必须大事务提交成功，内部嵌套的事务才能提交成功。如果失败了，可以回滚嵌套的事务。

注意：嵌套事务不应在gorm中大量使用，因为其不支持预编译。

func NestTransaction() {t := Teacher{Name:   "yuan",Age:    41,Salary: 122345.123,Email:  "yuan@test.com",}t1 := Teacher{Name:   "yuan2",Age:    40,Salary: 12345.123,Email:  "yuan@test.com",,}t2 := Teacher{Name:   "yuan3",Age:    50,Salary: 12345.123,Email:  "yuan@test.com",,}DB.Transaction(func(tx *gorm.DB) error {if err := tx.Create(&t).Error; err != nil {return err}tx.Transaction(func(tx1 *gorm.DB) error {if err := tx1.Create(&t1).Error; err != nil {return err}return nil})tx.Transaction(func(tx1 *gorm.DB) error {if err := tx1.Create(&t2).Error; err != nil {return err}return nil})return nil})
}

手动事务

gorm也提供了begin, rollback等接口支持手动事务的操作

func ManualTransaction() {t := Teacher{Name:   "yuan",Age:    41,Salary: 122345.123,Email:  "yuan@test.com",}c := Course{Name:  "golang",Price: 12345.1234,}tx := DB.Begin()defer func() {if err := recover(); err != nil {tx.Rollback()}}()if tx.Error != nil {log.Fatal(tx.Error)return}if err := tx.Create(&t).Error; err != nil {tx.Rollback()return}c.UserID = t.IDif err := tx.Create(&c).Error; err != nil {tx.Rollback()return}tx.Commit()
}

检查点savePoint

gorm也提供了savePoint的机制来支持事务的分段提交，回滚到某个特定的savePoint（RollbackTo）

func SavePointTransaction() {t := Teacher{Name:   "yuan",Age:    41,Salary: 122345.123,Email:  "yuan@test.com",}c := Course{Name:  "golang",Price: 12345.1234,}tx := DB.Begin()defer func() {if err := recover(); err != nil {tx.Rollback()}}()if tx.Error != nil {log.Fatal(tx.Error)return}if err := tx.Create(&t).Error; err != nil {tx.Rollback()return}// 创建savepointtx.SavePoint("teacher")c.UserID = t.IDif err := tx.Create(&c).Error; err != nil {// 回滚到对应savepointtx.RollbackTo("teacher")return}tx.Commit()
}