Struct MemoryStore 

pub struct MemoryStore { /* private fields */ }

An in-memory VersionStore backed by a hash map of version chains.

Each key maps to its versions in ascending commit-timestamp order, so a snapshot read is a binary search for the newest version at or below the snapshot timestamp. This is the default store of Db::new and is well suited to caches, tests, and workloads that fit in memory.

MemoryStore is thread-safe and is meant to be shared: a Db holds it behind an Arc and clones that handle to every thread. Versions accumulate until garbage collection lands (a later roadmap phase), so a long-lived store under heavy overwrite grows without bound for now.

Examples

use txn_db::{Db, MemoryStore};

// `Db::new()` uses a `MemoryStore`; this is the explicit form.
let db = Db::with_store(MemoryStore::new());
let mut tx = db.begin();
tx.put(b"hello".to_vec(), b"world".to_vec());
tx.commit()?;

Implementations

impl MemoryStore

pub fn new() -> Self

Create an empty in-memory store.

Examples

use txn_db::MemoryStore;

let store = MemoryStore::new();

pub fn key_count(&self) -> usize

Number of distinct keys that have ever been written.

Counts keys, not versions, and includes keys whose latest version is a tombstone. Primarily useful in tests and diagnostics.

Examples

use txn_db::{Db, MemoryStore};

let store = MemoryStore::new();
assert_eq!(store.key_count(), 0);

Trait Implementations

impl Debug for MemoryStore

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

Formats the value using the given formatter.

impl Default for MemoryStore

fn default() -> MemoryStore

Returns the “default value” for a type.

impl VersionStore for MemoryStore

fn get(&self, key: &[u8], read_ts: Timestamp) -> Result<Option<Arc<[u8]>>>

Return the value of key visible at read_ts.

fn latest_commit_ts(&self, key: &[u8]) -> Result<Option<Timestamp>>

Return the commit timestamp of the most recent version of key.

fn apply(&self, commit_ts: Timestamp, writes: Vec<WriteEntry>) -> Result<()>

Install a batch of versions at commit_ts.