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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 databasefunc (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 dbfunc (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