Struct WalTxn 

pub struct WalTxn<'a, F: FileBackend = FileHandle> { /* private fields */ }

An in-progress WAL transaction.

Buffers (page_id, page_body) pairs in memory; the actual disk writes happen at WalTxn::commit. This is how group commit works: many calls to WalTxn::append amortise one sync_data.

Implementations

impl<F: FileBackend> WalTxn<'_, F>

pub fn append(&mut self, page_id: PageId, page: &Page) -> Result<()>

Append (page_id, page) to the transaction. The frame is held in memory until WalTxn::commit.

Errors

Returns Error::InvalidArgument if the resulting WAL size would exceed Config::wal_size_limit.

pub fn append_header(&mut self, page: &Page) -> Result<()>

M6 #51: append a file-header (page-0) frame to the transaction. The WAL frame carries page_id = 0; recovery’s WalkState::absorb routes it into a dedicated header slot. Used by crate::pager::Pager::commit when crate::pager::Pager::set_root_catalog dirtied the in-memory header.

Errors

As Self::append.

pub fn staged_frame_count(&self) -> usize

Number of frames currently staged in this transaction.

pub fn commit(self) -> Result<Lsn>

Commit the transaction. Writes every staged frame to disk, stamps the last one as the commit marker, performs one sync_data(sync_mode), and returns the LSN of the last frame.

An empty transaction is a no-op and returns the current next_lsn - 1.

Errors

Returns Error::Io on syscall failure.

pub fn drain_staged(self) -> Vec<(PageId, Page)>

Drain the staged frames into an owned Vec so the pager can merge them into its in-memory view after a successful commit. Called by WalTxn::commit_returning_view (see pager::commit).

Trait Implementations

impl<'a, F: Debug + FileBackend> Debug for WalTxn<'a, F>

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

Formats the value using the given formatter.