storage

A sessioned Merkle key/value store

The crate was designed to be the blockchain state database. It provides persistent storage layer for key-value pairs on top of Nomic Merk.

FEATURES:

• Key-value updates(in a transaction) applied to storage can be reverted if transaction fails.
• Key-value updates(in a block) applied to storage can be reverted if block fails to commit.
• Prefix-based key-value iteration on committed state.
• Prefix-based key-value iteration on latest state.
• Versioned key-value pairs available for queries.
• Entire chain-state available as a batch of key-value pairs at any height within version window.
• Root hash calculation.

Example:

[dependencies]
storage = { git = "ssh://git@github.com/FindoraNetwork/storage.git", tag = "v0.2.0" }
fin_db = { git = "ssh://git@github.com/FindoraNetwork/storage.git", tag = "v0.2.0" }
parking_lot = "0.12"

use storage::state::{ChainState, State, PrefixedStore};
use storage::store::traits::{Stated, Store};
use fin_db::FinDB;
use parking_lot::RwLock;
use std::sync::Arc;
use std::thread;

// This window is used to determine how many versions of each KV pair are to be kept in the
// auxiliary db.
const VER_WINDOW:u64 = 100;

fn main() {
    println!("Testing Prefixed Store!");
    prefixed_store();
}

fn prefixed_store() {
    // create store
    let path = thread::current().name().unwrap().to_owned();
    let fdb = FinDB::open(path).expect("failed to open db");
    let cs = Arc::new(RwLock::new(ChainState::new(fdb, "test_db".to_string(), VER_WINDOW)));
    let mut state = State::new(cs);
    let mut store = PrefixedStore::new("my_store", &mut state);
    let hash0 = store.state().root_hash();

    // set kv pairs and commit
    store.set(b"k10", b"v10".to_vec());
    store.set(b"k20", b"v20".to_vec());
    let (hash1, _height) = store.state_mut().commit(1).unwrap();

    // verify
    assert_eq!(store.get(b"k10").unwrap(), Some(b"v10".to_vec()));
    assert_eq!(store.get(b"k20").unwrap(), Some(b"v20".to_vec()));
    assert_ne!(hash0, hash1);

    // add, delete and update
    store.set(b"k10", b"v15".to_vec());
    store.delete(b"k20").unwrap();
    store.set(b"k30", b"v30".to_vec());

    // verify
    assert_eq!(store.get(b"k10").unwrap(), Some(b"v15".to_vec()));
    assert_eq!(store.get(b"k20").unwrap(), None);
    assert_eq!(store.get(b"k30").unwrap(), Some(b"v30".to_vec()));

    // rollback and verify
    store.state_mut().discard_session();
    assert_eq!(store.get(b"k10").unwrap(), Some(b"v10".to_vec()));
    assert_eq!(store.get(b"k20").unwrap(), Some(b"v20".to_vec()));
    assert_eq!(store.get(b"k30").unwrap(), None);

    // get previous version of a key value pair
    store.set(b"k10", b"v25".to_vec());
    let _ = store.state_mut().commit(2);
    assert_eq!(store.get(b"k10").unwrap(), Some(b"v25".to_vec()));
    assert_eq!(store.get_v(b"k10", 1).unwrap(), Some(b"v10".to_vec()));
}