code: func matchPrefix(row chunk.Row, colIdx int, ad *types.Datum) bool {
  	switch ad.Kind() {
  	case types.KindString, types.KindBytes, types.KindBinaryLiteral, types.KindMysqlBit:
  		return strings.HasPrefix(row.GetString(colIdx), ad.GetString())
  	}
  	return false
  }
docs: // matchPrefix checks whether ad is the prefix of value