Struct LogFileHeader 

pub struct LogFileHeader {
    pub format_version: u32,
    pub start_lsn: u64,
    pub log_uuid: u32,
    pub created_by: String,
}

Log file header (block 0 of the redo log file).

The header layout changed in MySQL 8.0.30 (format version 6):

Offset	Pre-8.0.30	8.0.30+ (incl. 9.x)
0	group_id (u32)	format_version (u32)
4	start_lsn (u64)	log_uuid (u32)
8	(start_lsn cont.)	start_lsn (u64)
12	file_no (u32)	(start_lsn cont.)
16	created_by (32 bytes)	created_by (32 bytes)

The format_version and group_id fields share offset 0; in practice, format version values 1-6 are distinguishable from typical group IDs.

Fields

format_version: u32

Log format version (offset 0).

In MySQL < 8.0.30 this was the log group ID. In 8.0.30+ this is the format version number (e.g. 6 for MySQL 8.0.30+, 9.0, 9.1). Aliased as group_id for backward compatibility.

start_lsn: u64

Start LSN of this log file.

log_uuid: u32

Log UUID (MySQL 8.0.30+) or 0 for older formats.

A 4-byte identifier for the data directory, stored at offset 4.

created_by: String

MySQL version string that created this log file (e.g. “MySQL 9.0.1”).

Implementations

impl LogFileHeader

pub fn group_id(&self) -> u32

Backward-compatible accessor: returns format_version as the group ID.

In MySQL < 8.0.30, offset 0 stored the log group ID. In 8.0.30+ it stores the format version. This accessor preserves API compatibility.

pub fn parse(block: &[u8]) -> Option<Self>

Parse a log file header from the first 512-byte block.

Handles both pre-8.0.30 and 8.0.30+ header layouts. The format is auto-detected: format version >= 6 indicates the 8.0.30+ layout where offset 4 is the log UUID and offset 8 is the start LSN. Versions 1-5 use the pre-8.0.30 layout where offset 4 is the start LSN (u64) and offset 12 is the file number.

Examples

use idb::innodb::log::{LogFileHeader, LOG_BLOCK_SIZE,
    LOG_HEADER_FORMAT, LOG_HEADER_START_LSN,
    LOG_HEADER_LOG_UUID, LOG_HEADER_CREATED_BY};
use byteorder::{BigEndian, ByteOrder};

// MySQL 8.0.30+ / 9.x format (format_version = 6)
let mut block = vec![0u8; LOG_BLOCK_SIZE];
BigEndian::write_u32(&mut block[LOG_HEADER_FORMAT..], 6);
BigEndian::write_u32(&mut block[LOG_HEADER_LOG_UUID..], 0x12345678);
BigEndian::write_u64(&mut block[LOG_HEADER_START_LSN..], 0x1000);
block[LOG_HEADER_CREATED_BY..LOG_HEADER_CREATED_BY + 12]
    .copy_from_slice(b"MySQL 9.0.1\0");

let hdr = LogFileHeader::parse(&block).unwrap();
assert_eq!(hdr.format_version, 6);
assert_eq!(hdr.start_lsn, 0x1000);
assert_eq!(hdr.log_uuid, 0x12345678);
assert_eq!(hdr.created_by, "MySQL 9.0.1");

Trait Implementations

impl Clone for LogFileHeader

fn clone(&self) -> LogFileHeader

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LogFileHeader

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Serialize for LogFileHeader

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.