Struct Header 

pub struct Header {
    pub lsn: Option<XLogRecPtr>,
    pub checksum: u16,
    pub flags: PageFlags,
    pub lower: LocationIndex,
    pub upper: LocationIndex,
    pub special: LocationIndex,
    pub pagesize_version: u16,
    pub prune_xid: Option<TransactionId>,
}

Fields

lsn: Option<XLogRecPtr>

Log Sequence Number: Position in the WAL just past the last record that changed the page, or None (stored as 0) if no record has, as on a page fresh from Page::init. See WAL Internals.

checksum: u16

flags: PageFlags

lower: LocationIndex

Offset of the start of free space, just past the last line pointer.

upper: LocationIndex

Offset of the end of free space, where tuple data begins.

special: LocationIndex

Offset of the start of the special space, which the access method reserves. See Database Page Layout.

pagesize_version: u16

Page size in the high bits, layout version in the low byte.

prune_xid: Option<TransactionId>

Oldest transaction whose deletions on this page could be pruned, or None (stored as 0) if there are none. Postgres only treats it as a hint, and leaves it unused on index pages. See Heap-Only Tuples (HOT), and chapter 5, “Page Pruning and HOT Updates”, of PostgreSQL 14 Internals by Egor Rogov.

Implementations

impl Header

pub fn try_from_raw(raw: &[u8; 24]) -> Result<Self, InvalidHeader>

Parses a header, with the checks Postgres runs before letting a page into the buffer pool. They don’t prove the header right, only plausible.

Trait Implementations

impl Clone for Header

fn clone(&self) -> Header

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Header

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

Formats the value using the given formatter.

impl PartialEq for Header

fn eq(&self, other: &Header) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for Header

impl Eq for Header

impl StructuralPartialEq for Header