code: func (b *builtinIsIPv4CompatSig) evalInt(row chunk.Row) (int64, bool, error) {
  	val, isNull, err := b.args[0].EvalString(b.ctx, row)
  	if err != nil || isNull {
  		return 0, err != nil, err
  	}
  
  	ipAddress := []byte(val)
  	if len(ipAddress) != net.IPv6len {
  		//Not an IPv6 address, return false
  		return 0, false, nil
  	}
  
  	prefixCompat := []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
  	if !bytes.HasPrefix(ipAddress, prefixCompat) {
  		return 0, false, nil
  	}
  	return 1, false, nil
  }
docs: // evalInt evals Is_IPv4_Compat
  // See https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_is-ipv4-compat