vitessio/vitess · error

Not implemented, post_header_length!=8

Error message

Not implemented, post_header_length!=8

What it means

NewTableMapEvent can only synthesize a table-map binlog event when the binlog format's post-header length for table-map events is 8 bytes. If the format declares a different header size, the builder panics because the encoding logic only supports the 8-byte layout.

Source

Thrown at go/mysql/binlog_event_make.go:333

	data[10] = byte(gtid.Domain >> 16)
	data[11] = byte(gtid.Domain >> 24)

	const FLStandalone = 1
	var flags2 byte
	if !hasBegin {
		flags2 |= FLStandalone
	}
	data[12] = flags2

	ev := s.Packetize(f, eMariaGTIDEvent, 0, data)
	return NewMariadbBinlogEvent(ev)
}

// NewTableMapEvent returns a TableMap event.
// Only works with post_header_length=8.
func NewTableMapEvent(f BinlogFormat, s *FakeBinlogStream, tableID uint64, tm *TableMap) BinlogEvent {
	if f.HeaderSize(eTableMapEvent) != 8 {
		panic("Not implemented, post_header_length!=8")
	}

	metadataLength := metadataTotalLength(tm.Types)

	length := 6 + // table_id
		2 + // flags
		1 + // schema name length
		len(tm.Database) +
		1 + // [00]
		1 + // table name length
		len(tm.Name) +
		1 + // [00]
		lenEncIntSize(uint64(len(tm.Types))) + // column-count len enc
		len(tm.Types) +
		lenEncIntSize(uint64(metadataLength)) + // lenenc-str column-meta-def
		metadataLength +
		len(tm.CanBeNull.data)
	data := make([]byte, length)

View on GitHub (pinned to 01a25a7d17)

Solutions

  1. Configure the BinlogFormat so the table-map event header size is 8 (as produced by MySQL 5.1+/MariaDB with row-based replication).
  2. Parse the format from a real Format Description event instead of hard-coding header sizes.
  3. If you must support other header sizes, extend NewTableMapEvent rather than reusing it.

Example fix

// before
f.HeaderSize[eTableMapEvent] = 6
ev := mysql.NewTableMapEvent(f, s, tableID, tm) // panics
// after
f.HeaderSize[eTableMapEvent] = 8
ev := mysql.NewTableMapEvent(f, s, tableID, tm)
Defensive patterns

Strategy: validation

Validate before calling

if f.HeaderSize(mysql.ETableMapEvent) != 8 {
    return errors.New("table-map post_header_length must be 8")
}
ev := mysql.NewTableMapEvent(f, s, tableID, tm)

Try / catch

func makeTableMap(f mysql.BinlogFormat, s *mysql.FakeBinlogStream, id uint64, tm *mysql.TableMap) (ev mysql.BinlogEvent, err error) {
    defer func() {
        if r := recover(); r != nil {
            err = fmt.Errorf("NewTableMapEvent: %v", r)
        }
    }()
    return mysql.NewTableMapEvent(f, s, id, tm), nil
}

Prevention

When it happens

Trigger: Calling mysql.NewTableMapEvent with a BinlogFormat whose HeaderSize(eTableMapEvent) is not 8 (e.g. a fake format built with a 6-byte post-header length).

Common situations: Unit tests or tools constructing binlog events with hand-crafted BinlogFormat values copied from a different event type or an older MySQL/MariaDB flavor; misconfigured fake streams in test harnesses.

Related errors

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/8fa6c352c1b542be. Report an issue: GitHub.