Gorm mysql Pluck 无法使用decimal

GORM Playground Link

https://github.com/go-gorm/playground/pull/437

Description

wallet := UserWallet{UserID: 1, Balance: decimal.NewFromFloat(99.60)}

    if err := DB.Create(&wallet).Error; err != nil {
        t.Errorf("Failed, got error: %v", err)
    }

    var balance decimal.Decimal
    if err := DB.Model(&UserWallet{}).Limit(1).Pluck("balance", &balance).Error; err != nil {
        t.Errorf("Failed, got error: %v", err)
    }

    if err := DB.Model(&UserWallet{}).Limit(1).Pluck("balance", balance).Error; err != nil {
        t.Errorf("Failed, got error: %v", err)
    }

错误：

sql: Scan error on column index 0, name "balance": destination not a pointer

Comment From: Heliner

check the https://gorm.io/docs/advanced_query.html , Pluck return mutilple values .

like this

var balance []decimal.Decimal if err := DB.Model(&UserWallet{}).Limit(1).Pluck("balance", &balance).Error; err != nil { t.Errorf("Failed, got error: %v", err) }

Comment From: liyuan1125

check the https://gorm.io/docs/advanced_query.html , Pluck return mutilple values .

like this

var balance []decimal.Decimal if err := DB.Model(&UserWallet{}).Limit(1).Pluck("balance", &balance).Error; err != nil { t.Errorf("Failed, got error: %v", err) }

var id uint64
if err := DB.Model(&UserWallet{}).Limit(1).Pluck("id", &id).Error; err != nil {
   t.Errorf("Failed, got error: %v", err)
}
fmt.Print(id)

output

1

Comment From: Heliner

this cause by Scan.scan() function args this func set this db raw data into result or results, when the type is uint64 or uint32 ... that set this last query raw data into result, when the type is an arrry or slice .. that set this all query raw data into results

var id uint64
if err := DB.Model(&UserWallet{}).Limit(1).Pluck("id", &id).Error; err != nil {
   t.Errorf("Failed, got error: %v", err)
}
fmt.Print(id)

you can use Pluck like this but if limit (n=..), n is greater than 1, an unexpect result will return

    wallet := UserWallet{UserID: 1, Balance: decimal.NewFromFloat(99.60)}
    wallet2 := UserWallet{UserID: 2, Balance: decimal.NewFromFloat(100.60)}

    if err := DB.Create(&wallet).Error; err != nil {
        t.Errorf("Failed, got error: %v", err)
    }
    if err := DB.Create(&wallet2).Error; err != nil {
        t.Errorf("Failed, got error: %v", err)
    }

    var id2 uint64
    if err := DB.Model(&UserWallet{}).Limit(2).Pluck("id", &id2).Error; err != nil {
        t.Errorf("Failed, got error: %v", err)
    }
    fmt.Printf("id:%v", id2)

so, you can use Limit(1).Pluck("id", &id) ,I don't known that is a feature or bug , but that is a special case and doc not recommand use Pluck do like this

Comment From: liyuan1125

this cause by Scan.scan() function args this func set this db raw data into result or results, when the type is uint64 or uint32 ... that set this last query raw data into result, when the type is an arrry or slice .. that set this all query raw data into results

var id uint64 if err := DB.Model(&UserWallet{}).Limit(1).Pluck("id", &id).Error; err != nil { t.Errorf("Failed, got error: %v", err) } fmt.Print(id)

you can use Pluck like this but if limit (n=..), n is greater than 1, an unexpect result will return

``` wallet := UserWallet{UserID: 1, Balance: decimal.NewFromFloat(99.60)} wallet2 := UserWallet{UserID: 2, Balance: decimal.NewFromFloat(100.60)}

if err := DB.Create(&wallet).Error; err != nil { t.Errorf("Failed, got error: %v", err) } if err := DB.Create(&wallet2).Error; err != nil { t.Errorf("Failed, got error: %v", err) }

var id2 uint64 if err := DB.Model(&UserWallet{}).Limit(2).Pluck("id", &id2).Error; err != nil { t.Errorf("Failed, got error: %v", err) } fmt.Printf("id:%v", id2) ```

so, you can use Limit(1).Pluck("id", &id) ,I don't known that is a feature or bug , but that is a special case and doc not recommand use Pluck do like this

I think its a bug https://github.com/go-gorm/gorm/issues/4457