func (db *DB) CreateUniqueIndex(table interface{}, name string, names ...string) error {
	return db.createIndex(table, true, name, names...)
}
func (db *DB) CreateUniqueIndex(table interface{}, name string, names ...string) error {
	return db.createIndex(table, true, name, names...)
}
// CreateUniqueIndex creates the unique index into database.
// If table isn't direct/indirect struct, it returns error.