salamander-db

SQLite for event-sourced state — built first for agent memory.

An embedded event-sourcing engine. The append-only log is the only durable structure; everything else is a rebuildable projection. Replay, time-travel, and fork are first-class: rewind any session to step N, branch it, and run two futures against the same history.

Second story: crash-proof application state. The torn-tail rule makes "state that never logically existed" impossible after a kill — and the full history comes free.

use salamander::agent::{EventBody, KvProjection};
use salamander::{AgentDb, Projection};

let mut db = AgentDb::open("./mydata")?;
db.append("session-1", EventBody::Put { key: "k".into(), value: b"v".to_vec() })?;
db.commit()?;                                  // fsync; durable

// Everything else rebuilds from the log:
let kv: KvProjection = db.projection()?;       // full replay
let past: KvProjection = db.view_at(1)?;       // state as of offset 1 (time-travel)

Features

• Segmented append-only log — CRC32C framing, torn-tail truncation on open, atomic manifest, single-writer lock.
• Projections — deterministic folds of the log; KvProjection, SessionProjection, or your own via the Projection trait.
• Time-travel & fork — view_at(n); fork(ns, n) branches a session while the log stays linear.
• Payload-generic — Salamander<B> over any serde payload; a provided agent vocabulary, JsonDb for dynamic JSON, or bring your own enum.
• Query layer — live registered views with secondary indexes: get / range / prefix / by, maintained incrementally (never stale).
• Group commit — combinable byte/count/time commit policies.
• Crash-tested — a kill -9 harness asserts the core invariant across thousands of crashes.

Status

Phase 1 core + Phase 1.5 (payload-generic engine, query layer, group commit, dynamic-JSON payloads) complete. Single-writer, embedded, in-memory projections (persistence is Phase 2). Not multi-writer, not a SQL/query language, not a vector store — by design.

Roadmap, changelog, and runnable examples: https://github.com/rdelprete/salamander-db

License

MIT