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