code: func (col *CorrelatedColumn) EvalTime(ctx sessionctx.Context, row chunk.Row) (types.Time, bool, error) {
  	if col.Data.IsNull() {
  		return types.Time{}, true, nil
  	}
  	return col.Data.GetMysqlTime(), false, nil
  }
docs: // EvalTime returns DATE/DATETIME/TIMESTAMP representation of CorrelatedColumn.