unique, ok := columnType.Unique()
	if !ok || field.PrimaryKey {
		return nil // skip primary key
	}
	// By default, ColumnType's Unique is not affected by UniqueIndex, so we don't care about UniqueIndex.
	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
		// We're currently only receiving boolean values on `Unique` tag,
		// so the UniqueConstraint name is fixed
		constraint := m.DB.NamingStrategy.UniqueName(stmt.Table, field.DBName)

	if association.Error == nil {
		reflectValue := association.DB.Statement.ReflectValue
		rel := association.Relationship

		var oldBelongsToExpr clause.Expression
		// we have to record the old BelongsTo value
		if association.Unscope && rel.Type == schema.BelongsTo {
			var foreignFields []*schema.Field
			for _, ref := range rel.References {
				if !ref.OwnPrimaryKey {

	// In some db (e.g. MySQL), Unique and UniqueIndex are indistinguishable.
	// When a column has a (not Mul) UniqueIndex, Migrator always reports its gorm.ColumnType is Unique.
	// It causes field unnecessarily migration.
	// Therefore, we need to record the UniqueIndex on this column (exclude Mul UniqueIndex) for MigrateColumnUnique.
	UniqueIndex string
}

func (field *Field) BindName() string {
	return strings.Join(field.BindNames, ".")
}