Struct Snapshot 

pub struct Snapshot {
    pub xid: u64,
    pub in_progress: HashSet<u64>,
}

Immutable snapshot taken at transaction start or statement start.

Callers evaluate UnifiedEntity::is_visible(snapshot.xid) on every row returned from storage to filter out rows created by concurrent transactions that hadn’t committed when the snapshot was taken.

Fields

xid: u64

The snapshot’s xid — every row with xmin <= xid created before the snapshot is visible (assuming xmax hasn’t passed).

in_progress: HashSet<u64>

Transactions that were still active when the snapshot was taken. Their writes must be hidden even when xmin <= xid, because the writer hadn’t committed yet from this snapshot’s point of view.

Implementations

impl Snapshot

pub fn sees(&self, xmin: u64, xmax: u64) -> bool

Is a row with this xmin/xmax visible under this snapshot?

Delegates to super::visibility::is_visible — the deep module that owns the full MVCC visibility predicate. The aborted argument is empty here because Snapshot does not carry the manager-level aborted set; callers that need the rolled-back-writer rule should consult SnapshotManager directly, or evolve Snapshot to embed an aborted view.

Trait Implementations

impl Clone for Snapshot

fn clone(&self) -> Snapshot

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Snapshot

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

Formats the value using the given formatter.