/** Returns a string representation of the object. */
 @Override
 public String toString() {
   if (colType == null) {
     return null;
   }
   StringBuilder result = new StringBuilder();
   for (int i = 0; i < colType.length; i++) {
     result.append("Column ").append(i).append(":");
     if (colValue[i] != null) {
       result.append(
           colType[i] == BYTEA.getOID() ? byteArrayInString((byte[]) colValue[i]) : colValue[i]);
     }
     result.append("\n");
   }
   return result.toString();
 }
  @Override
  public void readFields(DataInput in) throws IOException {
    /*
     * extract pkt len.
     *
     * GPSQL-1107:
     * The DataInput might already be empty (EOF), but we can't check it beforehand.
     * If that's the case, pktlen is updated to -1, to mark that the object is still empty.
     * (can be checked with isEmpty()).
     */
    pktlen = readPktLen(in);
    if (isEmpty()) {
      return;
    }

    /* extract the version and col cnt */
    int version = in.readShort();
    int curOffset = 4 + 2;
    int colCnt;

    /* !!! Check VERSION !!! */
    if (version != GPDBWritable.VERSION && version != GPDBWritable.PREV_VERSION) {
      throw new IOException(
          "Current GPDBWritable version("
              + GPDBWritable.VERSION
              + ") does not match input version("
              + version
              + ")");
    }

    if (version == GPDBWritable.VERSION) {
      errorFlag = in.readByte();
      curOffset += 1;
    }

    colCnt = in.readShort();
    curOffset += 2;

    /* Extract Column Type */
    colType = new int[colCnt];
    DBType[] coldbtype = new DBType[colCnt];
    for (int i = 0; i < colCnt; i++) {
      int enumType = (in.readByte());
      curOffset += 1;
      if (enumType == DBType.BIGINT.ordinal()) {
        colType[i] = BIGINT.getOID();
        coldbtype[i] = DBType.BIGINT;
      } else if (enumType == DBType.BOOLEAN.ordinal()) {
        colType[i] = BOOLEAN.getOID();
        coldbtype[i] = DBType.BOOLEAN;
      } else if (enumType == DBType.FLOAT8.ordinal()) {
        colType[i] = FLOAT8.getOID();
        coldbtype[i] = DBType.FLOAT8;
      } else if (enumType == DBType.INTEGER.ordinal()) {
        colType[i] = INTEGER.getOID();
        coldbtype[i] = DBType.INTEGER;
      } else if (enumType == DBType.REAL.ordinal()) {
        colType[i] = REAL.getOID();
        coldbtype[i] = DBType.REAL;
      } else if (enumType == DBType.SMALLINT.ordinal()) {
        colType[i] = SMALLINT.getOID();
        coldbtype[i] = DBType.SMALLINT;
      } else if (enumType == DBType.BYTEA.ordinal()) {
        colType[i] = BYTEA.getOID();
        coldbtype[i] = DBType.BYTEA;
      } else if (enumType == DBType.TEXT.ordinal()) {
        colType[i] = TEXT.getOID();
        coldbtype[i] = DBType.TEXT;
      } else {
        throw new IOException("Unknown GPDBWritable.DBType ordinal value");
      }
    }

    /* Extract null bit array */
    byte[] nullbytes = new byte[getNullByteArraySize(colCnt)];
    in.readFully(nullbytes);
    curOffset += nullbytes.length;
    boolean[] colIsNull = byteArrayToBooleanArray(nullbytes, colCnt);

    /* extract column value */
    colValue = new Object[colCnt];
    for (int i = 0; i < colCnt; i++) {
      if (!colIsNull[i]) {
        /* Skip the alignment padding */
        int skipbytes = roundUpAlignment(curOffset, coldbtype[i].getAlignment()) - curOffset;
        for (int j = 0; j < skipbytes; j++) {
          in.readByte();
        }
        curOffset += skipbytes;

        /* For fixed length type, increment the offset according to type type length here.
         * For var length type (BYTEA, TEXT), we'll read 4 byte length header and the
         * actual payload.
         */
        int varcollen = -1;
        if (coldbtype[i].isVarLength()) {
          varcollen = in.readInt();
          curOffset += 4 + varcollen;
        } else {
          curOffset += coldbtype[i].getTypeLength();
        }

        switch (DataType.get(colType[i])) {
          case BIGINT:
            {
              colValue[i] = in.readLong();
              break;
            }
          case BOOLEAN:
            {
              colValue[i] = in.readBoolean();
              break;
            }
          case FLOAT8:
            {
              colValue[i] = in.readDouble();
              break;
            }
          case INTEGER:
            {
              colValue[i] = in.readInt();
              break;
            }
          case REAL:
            {
              colValue[i] = in.readFloat();
              break;
            }
          case SMALLINT:
            {
              colValue[i] = in.readShort();
              break;
            }

            /* For BYTEA column, it has a 4 byte var length header. */
          case BYTEA:
            {
              colValue[i] = new byte[varcollen];
              in.readFully((byte[]) colValue[i]);
              break;
            }
            /* For text formatted column, it has a 4 byte var length header
             * and it's always null terminated string.
             * So, we can remove the last "\0" when constructing the string.
             */
          case TEXT:
            {
              byte[] data = new byte[varcollen];
              in.readFully(data, 0, varcollen);
              colValue[i] = new String(data, 0, varcollen - 1, CHARSET);
              break;
            }

          default:
            throw new IOException("Unknown GPDBWritable ColType");
        }
      }
    }

    /* Skip the ending alignment padding */
    int skipbytes = roundUpAlignment(curOffset, 8) - curOffset;
    for (int j = 0; j < skipbytes; j++) {
      in.readByte();
    }
    curOffset += skipbytes;

    if (errorFlag != 0) {
      throw new IOException("Received error value " + errorFlag + " from format");
    }
  }