Struct VersionChain 

pub struct VersionChain<T> { /* private fields */ }

A chain of versions for a single entity.

Versions are stored newest-first for efficient access to recent versions. Old versions can be garbage collected when no active transactions can see them.

Implementations

impl<T> VersionChain<T>

pub fn new() -> VersionChain<T>

Creates a new empty version chain.

pub fn with_initial( data: T, created_epoch: EpochId, created_by: TxId, ) -> VersionChain<T>

Creates a version chain with an initial version.

pub fn add_version(&mut self, data: T, created_epoch: EpochId, created_by: TxId)

Adds a new version to the chain.

The new version becomes the head of the chain.

pub fn visible_at(&self, epoch: EpochId) -> Option<&T>

Finds the version visible at the given epoch.

Returns a reference to the visible version’s data, or None if no version is visible at that epoch.

pub fn visible_to(&self, epoch: EpochId, tx: TxId) -> Option<&T>

Finds the version visible to a specific transaction.

This considers both the transaction’s epoch and its own uncommitted changes.

pub fn mark_deleted(&mut self, delete_epoch: EpochId) -> bool

Marks the current visible version as deleted.

Returns true if a version was marked, false if no visible version exists.

pub fn modified_by(&self, tx: TxId) -> bool

Checks if any version was modified by the given transaction.

pub fn remove_versions_by(&mut self, tx: TxId)

Removes all versions created by the given transaction.

Used for rollback to discard uncommitted changes.

pub fn has_conflict(&self, start_epoch: EpochId, our_tx: TxId) -> bool

Checks if there’s a concurrent modification conflict.

A conflict exists if another transaction modified this entity after our start epoch.

pub fn version_count(&self) -> usize

Returns the number of versions in the chain.

pub fn is_empty(&self) -> bool

Returns true if the chain has no versions.

pub fn gc(&mut self, min_epoch: EpochId)

Garbage collects old versions that are no longer visible to any transaction.

Keeps versions that might still be visible to transactions at or after min_epoch.

pub fn latest(&self) -> Option<&T>

Returns a reference to the latest version’s data regardless of visibility.

pub fn latest_mut(&mut self) -> Option<&mut T>

Returns a mutable reference to the latest version’s data.

impl<T> VersionChain<T>

where T: Clone,

pub fn get_mut( &mut self, epoch: EpochId, tx: TxId, modify_epoch: EpochId, ) -> Option<&mut T>

Gets a mutable reference to the visible version’s data for modification.

If the version is not owned by this transaction, creates a new version with a copy of the data.

Trait Implementations

impl<T> Clone for VersionChain<T>

where T: Clone,

fn clone(&self) -> VersionChain<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> Debug for VersionChain<T>

where T: Debug,

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

Formats the value using the given formatter.

impl<T> Default for VersionChain<T>

fn default() -> VersionChain<T>

Returns the “default value” for a type.