code: func initDBPrivEntry(ctx sessionctx.Context, user string, host string, db string) error {
  	sql := fmt.Sprintf(`INSERT INTO %s.%s (Host, User, DB) VALUES ('%s', '%s', '%s')`, mysql.SystemDB, mysql.DBTable, host, user, db)
  	_, _, err := ctx.(sqlexec.RestrictedSQLExecutor).ExecRestrictedSQL(ctx, sql)
  	return err
  }
docs: // initDBPrivEntry inserts a new row into mysql.DB with empty privilege.