Tablestore:PlainBuffer

Format definition

A PlainBuffer message is a header followed by one or more rows. Each row contains a primary key section and an attribute column section — both can be optional depending on the operation (see grammar below). Tags act as field delimiters — each tag tells the parser what comes next, so the parser can advance through the byte stream without ambiguity.

plainbuffer = tag_header row1  [row2]  [row3]
row = ( pk [attr] | [pk] attr | pk attr ) [tag_delete_marker] row_checksum;
pk = tag_pk cell_1 [cell_2] [cell_3]
attr  = tag_attr cell1 [cell_2] [cell_3]
cell = tag_cell cell_name [cell_value] [cell_op] [cell_ts] cell_checksum
cell_name = tag_cell_name  formated_value
cell_value = tag_cell_value formated_value
cell_op = tag_cell_op  cell_op_value
cell_ts = tag_cell_ts cell_ts_value
row_checksum = tag_row_checksum row_crc8
cell_checksum = tag_cell_checksum row_crc8

formated_value = value_type value_len value_data
value_type = int8
value_len = int32

cell_op_value = delete_all_version | delete_one_version
cell_ts_value = int64 
delete_all_version = 0x01 (1byte)
delete_one_version = 0x03 (1byte)
                

Tag values

Most tags are a single byte that marks the start of a field; tag_header is 4 bytes. The parser reads the tag, determines what field follows, reads the appropriate number of bytes, and advances to the next tag.

tag_header = 0x75 (4byte)
tag_pk = 0x01 (1byte)
tag_attr = 0x02 (1byte)
tag_cell = 0x03 (1byte)
tag_cell_name = 0x04 (1byte)
tag_cell_value = 0x05 (1byte)
tag_cell_op = 0x06 (1byte)
tag_cell_ts = 0x07 (1byte)
tag_delete_marker = 0x08 (1byte)
tag_row_checksum = 0x09 (1byte)
tag_cell_checksum = 0x0A (1byte)
            

ValueType values

Valid values for value_type in formated_value:

VT_INTEGER = 0x0
VT_DOUBLE = 0x1
VT_BOOLEAN = 0x2
VT_STRING = 0x3
VT_NULL = 0x6
VT_BLOB = 0x7
VT_INF_MIN = 0x9
VT_INF_MAX = 0xa
VT_AUTO_INCREMENT = 0xb
            

Checksum calculation

Checksums use CRC8. The calculation follows this logic:

• Each cell's name, value, type, and timestamp contribute to that cell's checksum.

• Each row's delete marker contributes a single byte: 0x1 if the row has a delete marker, 0x0 if it does not.

• The row checksum is computed by running CRC8 over the individual cell checksums — not over the raw cell data.

public static byte getChecksum(byte crc, PlainBufferCell cell) throws IOException {

    if (cell.hasCellName()) {
        crc = crc8(crc, cell.getNameRawData());
    }

    if (cell.hasCellValue()) {
        if (cell.isPk()) {
            crc = cell.getPkCellValue().getChecksum(crc);
        } else {
            crc = cell.getCellValue().getChecksum(crc);
        }
    }

    if (cell.hasCellTimestamp()) {
        crc = crc8(crc, cell.getCellTimestamp());
    }

    if (cell.hasCellType()) {
        crc = crc8(crc, cell.getCellType());
    }

    return crc;
}

public static byte getChecksum(byte crc, PlainBufferRow row) throws IOException {
    for (PlainBufferCell cell : row.getPrimaryKey()) {
        crc = crc8(crc, cell.getChecksum());
    }

    for (PlainBufferCell cell : row.getCells()) {
        crc = crc8(crc, cell.getChecksum());
    }

    byte del = 0;
    if (row.hasDeleteMarker()) {
        del = (byte)0x1;
    }
    crc = crc8(crc, del);

    return crc;
}
            

Example

The following row has two primary key columns and four attribute columns.

• Primary key columns:

  • [pk1:string:iampk]

  • [pk2:integer:100]

• Attribute columns:

  • [column1:string:bad:1001]

  • [column2:integer:128:1002]

  • [column3:double:34.2:1003]

  • [column4:del_all_versions]

<The start position for headers>[0x75]
<The start position for primary key columns>[0x1]
  <Cell1>[0x3][0x4][0x3][3][pk1][0x5][0x3][5][iampk][_cell_checksum]
  <Cell2>[0x3][0x4][0x3][3][pk2][0x5][0x0][8][100][_cell_checksum]
<The start position for attribute columns>[0x2]
  <Cell1>[0x3][0x4][0x3][7][column1][0x5][0x3][3][bad][0x7][1001][_cell_checksum]
  <Cell2>[0x3][0x4][0x3][7][column2][0x5][0x0][8][128][0x7][1002][_cell_checksum]
  <Cell3>[0x3][0x4][0x3][7][column3][0x5][0x1][8][34.2][0x7][1003][_cell_checksum]
  <Cell4>[0x3][0x4][0x3][7][column4][0x6][1][_cell_checksum]
[_row_check_sum]