func (m Migrator) MigrateColumn(value interface{}, field *schema.Field, columnType gorm.ColumnType) error {
	if field.IgnoreMigration {
		return nil
	}

	// found, smart migrate
	fullDataType := strings.TrimSpace(strings.ToLower(m.DB.Migrator().FullDataTypeOf(field).SQL))
	realDataType := strings.ToLower(columnType.DatabaseTypeName())

	var (
		alterColumn bool
		isSameType  = fullDataType == realDataType
	)

		typeName = polymorphic + "Type"
		typeId   = polymorphic + "ID"
	)

	if value, ok := field.TagSettings["POLYMORPHICTYPE"]; ok {
		typeName = strings.TrimSpace(value)
	}

	if value, ok := field.TagSettings["POLYMORPHICID"]; ok {
		typeId = strings.TrimSpace(value)
	}

	relation.Polymorphic.PolymorphicType = relation.FieldSchema.FieldsByName[typeName]

	}

	if s, ok := field.TagSettings["SCALE"]; ok {
		field.Scale, _ = strconv.Atoi(s)
	}

	// default value is function or null or blank (primary keys)
	field.DefaultValue = strings.TrimSpace(field.DefaultValue)
	skipParseDefaultValue := strings.Contains(field.DefaultValue, "(") &&
		strings.Contains(field.DefaultValue, ")") || strings.ToLower(field.DefaultValue) == "null" || field.DefaultValue == ""