emdb 0.3.0 - Docs.rs

Status

Phase 2. This crate now provides file-backed persistence with crash recovery for a single append-only storage file. The API is still pre-1.0 and may change before 1.0.

Track progress and roadmap: https://github.com/jamesgober/emdb-rs

Installation

[dependencies]
emdb = "0.3"

Quick Start

use emdb::Emdb;

let mut db = Emdb::open_in_memory();
db.insert("name", "emdb")?;
assert_eq!(db.get("name")?, Some(b"emdb".to_vec()));
# Ok::<(), emdb::Error>(())

Persistence

use emdb::{Emdb, FlushPolicy};

let path = std::env::temp_dir().join("app.emdb");

{
    let mut db = Emdb::builder()
        .path(path.clone())
        .flush_policy(FlushPolicy::EveryN(64))
        .build()?;

    db.insert("user:1", "james")?;
    db.flush()?;
}

let reopened = Emdb::open(&path)?;
assert_eq!(reopened.get("user:1")?, Some(b"james".to_vec()));
# let _cleanup = std::fs::remove_file(path);
# Ok::<(), emdb::Error>(())

Manual compaction:

use emdb::Emdb;

let path = std::env::temp_dir().join("compact.emdb");
let mut db = Emdb::open(&path)?;
db.insert("k", "v")?;
db.compact()?;
db.flush()?;
# let _cleanup = std::fs::remove_file(path);
# Ok::<(), emdb::Error>(())

Features

ttl (default): per-record expiration and default TTL support.
nested: dotted-prefix group operations and Focus handles.
persistence (core): append-only file log, replay-on-open, flush policy, and compaction.

TTL Example

# #[cfg(feature = "ttl")]
# {
use std::time::Duration;

use emdb::{Emdb, Ttl};

let mut db = Emdb::builder()
    .default_ttl(Duration::from_secs(30))
    .build()?;
db.insert_with_ttl("session", "token", Ttl::Default)?;
assert!(db.ttl("session")?.is_some());
# }
# Ok::<(), emdb::Error>(())

Nested Example

# #[cfg(feature = "nested")]
# {
use emdb::Emdb;

let mut db = Emdb::open_in_memory();
let mut product = db.focus("product");
product.set("name", "phone")?;
product.set("price", "799")?;

assert_eq!(product.get("name")?, Some(b"phone".to_vec()));
assert_eq!(db.group("product").count(), 2);
# }
# Ok::<(), emdb::Error>(())

Goals

Embedded-first — runs in-process; no separate server, no network.
High performance — zero-copy reads, allocation-free hot paths, cache-friendly layout.
Safe — strict clippy profile, no unwrap in library code, all unsafe documented.
Small footprint — minimal dependency graph, fast compile times.
Portable — Linux, macOS, Windows (x86_64 and ARM64).

Non-Goals

Client-server operation (use a dedicated DBMS for that).
A full SQL dialect at this stage.
Distributed replication at this stage.

Related Projects

emdb is the Rust implementation. Implementations in other languages (Go, C, and others) are planned and will live under their own repositories.

License

Licensed under the Apache License, Version 2.0.