Enum ScanSinceEvent 

pub enum ScanSinceEvent {
    Insert {
        key: Slice,
        value: Slice,
        seqno: SeqNo,
    },
    MergeOperand {
        key: Slice,
        operand: Slice,
        seqno: SeqNo,
    },
    PointTombstone {
        key: Slice,
        seqno: SeqNo,
    },
    RangeTombstone {
        start_key: Slice,
        end_key: Slice,
        seqno: SeqNo,
    },
}

A single change event emitted by Tree::scan_since_seqno.

Each event carries the sequence number at which the change was committed. Events are emitted in increasing seqno order, so a downstream consumer (replica, Kafka connector, Debezium-style pipeline) can replay them in order to reconstruct the source’s history. Superseded versions are not collapsed: a key updated three times after the target seqno yields three events, mirroring the source’s full change history rather than just its latest visible state.

Replay semantics

Applying events in seqno order reconstructs the state delta. An Insert(K, V1, s=150) followed by a PointTombstone(K, s=200) means “K was inserted with V1 at 150, then deleted at 200” — the net effect on a replica starting before 150 is “create K with V1, then delete K”, matching the source.

Merge operands

A store using a MergeOperator records partial updates as MergeOperand events rather than resolved values: the consumer applies the same merge operator to reproduce the source’s state. Emitting a merge as an Insert would make a replica overwrite instead of merge, diverging from the source; resolving the merge chain here would require reading the full base+operand history and defeat the block-skip optimization, so the raw operand is surfaced instead.

KV-separated (blob) values

When a value is stored out-of-line in a blob file, the blob is resolved and the real value is carried in the Insert event, so the consumer never needs access to the source’s blob files to replicate.

Variants

Insert

A record was written (or overwritten) at seqno.

Covers both inline values and values resolved from a blob file.

Fields

key: Slice

User key that was written.

value: Slice

Value written at seqno (resolved from a blob file if the entry was KV-separated).

seqno: SeqNo

Sequence number at which the write was committed.

MergeOperand

A merge operand was written at seqno.

The consumer must apply the source’s MergeOperator to combine this operand with the prior value / operands, exactly as the source does.

Fields

key: Slice

User key the operand applies to.

operand: Slice

Raw merge operand bytes, to be combined via the merge operator.

seqno: SeqNo

Sequence number at which the operand was committed.

PointTombstone

A single key was deleted at seqno.

Covers both regular and weak (single-delete) tombstones; both reduce to “this key is gone as of seqno” for replay purposes.

Fields

key: Slice

User key that was deleted.

seqno: SeqNo

Sequence number at which the deletion was committed.

RangeTombstone

A half-open key range [start_key, end_key) was deleted at seqno.

Fields

start_key: Slice

Inclusive lower bound of the deleted range.

end_key: Slice

Exclusive upper bound of the deleted range.

seqno: SeqNo

Sequence number at which the range deletion was committed.

Implementations

impl ScanSinceEvent

pub fn seqno(&self) -> SeqNo

Sequence number at which this change was committed.

Events from Tree::scan_since_seqno arrive in increasing order of this value.

Trait Implementations

impl Clone for ScanSinceEvent

fn clone(&self) -> ScanSinceEvent

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ScanSinceEvent

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

Formats the value using the given formatter.

impl Eq for ScanSinceEvent

impl PartialEq for ScanSinceEvent

fn eq(&self, other: &ScanSinceEvent) -> 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 StructuralPartialEq for ScanSinceEvent