type ConstraintInterface interface {
	GetName() string
	Build() (sql string, vars []interface{})
}

// GormDataTypeInterface gorm data type interface
type GormDataTypeInterface interface {
	GormDataType() string
}

// FieldNewValuePool field new scan value pool
type FieldNewValuePool interface {
	Get() interface{}
	Put(interface{})
}

// CreateClausesInterface create clauses interface

		// use same data type for foreign keys
		if copyableDataType(primaryKeyField.DataType) {
			relation.Polymorphic.PolymorphicID.DataType = primaryKeyField.DataType
		}
		relation.Polymorphic.PolymorphicID.GORMDataType = primaryKeyField.GORMDataType
		if relation.Polymorphic.PolymorphicID.Size == 0 {
			relation.Polymorphic.PolymorphicID.Size = primaryKeyField.Size
		}

		relation.References = append(relation.References, &Reference{

		} else if strings.ToUpper(v) == "MILLI" {
			field.AutoUpdateTime = UnixMillisecond
		} else {
			field.AutoUpdateTime = UnixSecond
		}
	}

	if field.GORMDataType == "" {
		field.GORMDataType = field.DataType
	}

	if val, ok := field.TagSettings["TYPE"]; ok {
		switch DataType(strings.ToLower(val)) {
		case Bool, Int, Uint, Float, String, Time, Bytes:

	case []byte:
		return json.Unmarshal(value, l)
	default:
		return errors.New("not supported")
	}
}

type ExampleStruct struct {
	Name string
	Val  string
}

func (ExampleStruct) GormDataType() string {
	return "bytes"
}

func (s ExampleStruct) Value() (driver.Value, error) {
	if len(s.Name) == 0 {
		return nil, nil
	}
	// for test, has no practical meaning
	s.Name = ""

		f := joinSchema.LookUpField(ref.ForeignKey.DBName)
		if f == nil {
			return fmt.Errorf("missing field %s for join table", ref.ForeignKey.DBName)
		}

		f.DataType = ref.ForeignKey.DataType
		f.GORMDataType = ref.ForeignKey.GORMDataType
		if f.Size == 0 {
			f.Size = ref.ForeignKey.Size
		}
		ref.ForeignKey = f
	}

	for name, rel := range relation.JoinTable.Relationships.Relations {

			schema.FieldsWithDefaultDBValue = append(schema.FieldsWithDefaultDBValue, field)
		}
	}

	if field := schema.PrioritizedPrimaryField; field != nil {
		switch field.GORMDataType {
		case Int, Uint:
			if _, ok := field.TagSettings["AUTOINCREMENT"]; !ok {
				if !field.HasDefaultValue || field.DefaultValueInterface != nil {

			alterColumn = true
		} else if !dvNotNull && currentDefaultNotNull {
			// null -> default value
			alterColumn = true
		} else if currentDefaultNotNull || dvNotNull {
			switch field.GORMDataType {
			case schema.Time:
				if !strings.EqualFold(strings.TrimSuffix(dv, "()"), strings.TrimSuffix(field.DefaultValue, "()")) {
					alterColumn = true
				}
			case schema.Bool:
				v1, _ := strconv.ParseBool(dv)