Struct ReadVersion 

pub struct ReadVersion(/* private fields */);

Stable numeric cursor for a committed database state.

ReadVersion is the public identifier callers use when they want to open a Snapshot at a specific historical state. Values are database-scoped: a read version is meaningful only for the database lineage that produced it, even if another database happens to contain the same numeric value.

Use Db::latest_read_version to capture the newest visible state, and Db::snapshot_at to validate and pin a version before reading. Versions older than Db::oldest_retained_read_version are expired and must not be read by falling back to latest.

Examples

use trine_kv::{Db, DbOptions, ReadVersion};

let db = Db::open_sync(DbOptions::memory())?;
assert_eq!(db.latest_read_version(), ReadVersion::ZERO);

db.put_sync(b"k", b"v1")?;
let version = db.latest_read_version();
let keep_version = db.snapshot_at(version)?;

db.put_sync(b"k", b"v2")?;
let snapshot = db.snapshot_at(version)?;
assert_eq!(db.get_at_sync(&snapshot, b"k")?, Some(b"v1".to_vec()));
drop(keep_version);

Implementations

impl ReadVersion

pub const ZERO: Self

Read version for the empty database state before the first successful state-changing write.

pub const fn from_u64(value: u64) -> Self

Creates a read version from its stable numeric cursor value.

The value is suitable for application-owned cursors that were previously obtained from this same database lineage. Creating a ReadVersion from a number does not prove the version is still retained; call Db::snapshot_at to validate it before reading.

pub const fn as_u64(self) -> u64

Returns the stable numeric cursor value.

Applications may persist this value and later rebuild it with ReadVersion::from_u64. The number is a public cursor, not a promise about Trine’s internal commit allocation machinery.

Trait Implementations

impl Clone for ReadVersion

fn clone(&self) -> ReadVersion

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ReadVersion

impl Debug for ReadVersion

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

Formats the value using the given formatter.

impl Default for ReadVersion

fn default() -> ReadVersion

Returns the “default value” for a type.

impl Eq for ReadVersion

impl Hash for ReadVersion

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for ReadVersion

fn cmp(&self, other: &ReadVersion) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for ReadVersion

fn eq(&self, other: &ReadVersion) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl PartialOrd for ReadVersion

fn partial_cmp(&self, other: &ReadVersion) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralPartialEq for ReadVersion