code: func getColumnPriv(ctx sessionctx.Context, name string, host string, db string, tbl string, col string) (string, error) {
  	sql := fmt.Sprintf(`SELECT Column_priv FROM %s.%s WHERE User='%s' AND Host='%s' AND DB='%s' AND Table_name='%s' AND Column_name='%s';`, mysql.SystemDB, mysql.ColumnPrivTable, name, host, db, tbl, col)
  	rows, fields, err := ctx.(sqlexec.RestrictedSQLExecutor).ExecRestrictedSQL(ctx, sql)
  	if err != nil {
  		return "", err
  	}
  	if len(rows) < 1 {
  		return "", errors.Errorf("get column privilege fail for %s %s %s %s %s", name, host, db, tbl, col)
  	}
  	cPriv := ""
  	if fields[0].Column.Tp == mysql.TypeSet {
  		setVal := rows[0].GetSet(0)
  		cPriv = setVal.Name
  	}
  	return cPriv, nil
  }
docs: // getColumnPriv gets current column scope privilege set from mysql.Columns_priv.
  // Return Column_priv.