Struct ForkPoint 

pub struct ForkPoint {
    pub vid_hwm: u64,
    pub eid_hwm: u64,
    pub dataset_versions: BTreeMap<String, u64>,
    pub version_hwm: u64,
    pub parent_branch_versions: BTreeMap<String, u64>,
}

Parent state captured atomically at a fork point under flush_lock.

Holds the allocator high-water marks and every existing dataset’s Lance main-branch version at the instant the parent’s L0 was flushed. Because Writer::flush_and_capture_fork_point reads these while still holding flush_lock, no concurrent commit or flush can advance the allocator or any dataset tip between the flush and the reads. A fork built from these values therefore cannot collide VIDs with the parent nor inherit rows committed after the fork point.

Fields

vid_hwm: u64

Next vertex id the parent would allocate at the fork point.

eid_hwm: u64

Next edge id the parent would allocate at the fork point.

dataset_versions: BTreeMap<String, u64>

dataset_name → Lance main-branch version at the fork point.

Keys use the same dataset naming as the fork branch loop (vertices, edges, vertices_{label}, deltas_{type}_{dir}, adjacency_{type}_{dir}). A dataset with no .lance directory on disk at the fork point has no entry.

version_hwm: u64

Parent’s MVCC version high-water-mark at the fork point: the largest _version any inherited row can carry. A fork bootstraps its own version counter to this floor so a fork transaction’s _version <= pin read still sees inherited (base_paths) rows, while the fork’s own writes get versions above it.

parent_branch_versions: BTreeMap<String, u64>

dataset_name → parent branch version at the fork point, for a nested fork (a fork of a fork). Empty when the parent is the primary DB.

A nested fork must branch off its parent fork’s Lance branch tip, which advances independently of main (so dataset_versions, which tracks the main-branch version, is not usable there). Captured under flush_lock alongside dataset_versions so a concurrent parent commit+flush cannot advance the tip between capture and branch creation.

Trait Implementations

impl Clone for ForkPoint

fn clone(&self) -> ForkPoint

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ForkPoint

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

Formats the value using the given formatter.

impl Default for ForkPoint

fn default() -> ForkPoint

Returns the “default value” for a type.