关于golang:聊聊gorm的CreateInBatches

序

本文次要钻研一下 gorm 的 CreateInBatches

CreateInBatches

gorm.io/gorm@v1.20.11/finisher_api.go

// CreateInBatches insert the value in batches into database
func (db *DB) CreateInBatches(value interface{}, batchSize int) (tx *DB) {reflectValue := reflect.Indirect(reflect.ValueOf(value))

    switch reflectValue.Kind() {
    case reflect.Slice, reflect.Array:
        var rowsAffected int64
        tx = db.getInstance()
        tx.AddError(tx.Transaction(func(tx *DB) error {for i := 0; i < reflectValue.Len(); i += batchSize {
                ends := i + batchSize
                if ends > reflectValue.Len() {ends = reflectValue.Len()
                }

                subtx := tx.getInstance()
                subtx.Statement.Dest = reflectValue.Slice(i, ends).Interface()
                subtx.callbacks.Create().Execute(subtx)
                if subtx.Error != nil {return subtx.Error}
                rowsAffected += subtx.RowsAffected
            }
            return nil
        }))
        tx.RowsAffected = rowsAffected
    default:
        tx = db.getInstance()
        tx.Statement.Dest = value
        tx.callbacks.Create().Execute(tx)
    }
    return
}

CreateInBatches 会依据 batchSize 来调配进行 create，然而他们是在同一个事务的，其 rowsAffected 是每个批次的 rowsAffected 的累加

AddError

gorm.io/gorm@v1.20.11/gorm.go

// AddError add error to db
func (db *DB) AddError(err error) error {
    if db.Error == nil {db.Error = err} else if err != nil {db.Error = fmt.Errorf("%v; %w", db.Error, err)
    }
    return db.Error
}

tx.AddError 办法在 db.Error 为 nil 时间接更新为 err；不为 nil 时判断 err 是否为 nil，不为 nil 时才更新为 err

CommitOrRollbackTransaction

gorm.io/gorm@v1.20.11/callbacks/transaction.go

func CommitOrRollbackTransaction(db *gorm.DB) {
    if !db.Config.SkipDefaultTransaction {if _, ok := db.InstanceGet("gorm:started_transaction"); ok {
            if db.Error == nil {db.Commit()
            } else {db.Rollback()
            }
            db.Statement.ConnPool = db.ConnPool
        }
    }
}

CommitOrRollbackTransaction 办法会判断 db.Error，如果不为 nil 则执行 db.Rollback()

实例

func createInBatchesDemo(db *gorm.DB) {entities := []DemoEntity{
        {Name: "coco",},
        {Name: "bear",},
    }
    result := db.Debug().CreateInBatches(&entities, 1)
    b, _ := json.Marshal(entities)
    log.Println("data:", string(b))
    log.Println("result.RowsAffected:", result.RowsAffected, "result.Error:", result.Error)
}

输入

2021/01/16 22:28:55 /demo.go:71
[0.384ms] [rows:1] INSERT INTO `demo_entities` (`created_at`,`updated_at`,`deleted_at`,`name`) VALUES ("2021-01-16 22:28:55.774","2021-01-16 22:28:55.774",NULL,"coco")

2021/01/16 22:28:55 /demo.go:71
[0.055ms] [rows:1] INSERT INTO `demo_entities` (`created_at`,`updated_at`,`deleted_at`,`name`) VALUES ("2021-01-16 22:28:55.774","2021-01-16 22:28:55.774",NULL,"bear")
2021/01/16 22:28:55 data: [{"ID":7,"CreatedAt":"2021-01-16T22:28:55.7743+08:00","UpdatedAt":"2021-01-16T22:28:55.7743+08:00","DeletedAt":null,"Name":"coco"},{"ID":8,"CreatedAt":"2021-01-16T22:28:55.774794+08:00","UpdatedAt":"2021-01-16T22:28:55.774794+08:00","DeletedAt":null,"Name":"bear"}]
2021/01/16 22:28:55 result.RowsAffected: 2 result.Error: <nil>

小结

gorm 的 CreateInBatches 容许用户自定义 batchSize，它会依据 batchSize 来调配进行 create，然而他们是在同一个事务的，其 rowsAffected 是每个批次的 rowsAffected 的累加。

doc

• gorm