andelf / rust-rocksdb

rust wrapper for rocksdb

rust-rocksdb

This library has been tested against RocksDB 5.1.2 on Linux and macOS.

status

• basic open/put/get/delete/close
• rustic merge operator
• write batch (thanks @dgrnbrg!)
• save ponit
• compaction filter, style
• LRU cache
• destroy/repair
• iterator
• comparator
• snapshot
• column family operations
• prefix seek
• slicetransform
• rate limiter
• statistics
• recovery
• backup
• pause/continue background work
• windows support

Feedback and pull requests welcome! If a particular feature of RocksDB is important to you, please let us know by opening an issue, and we will prioritize it.

Prerequisite: RocksDB

First, use your system's package manager to install snappy. This is optional, but lets rocksdb take advantage of better compression, and some code may require it.

To install rocksdb, please refer to it's installation guide. For Windows users, please make sure you configure rocksdb with CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS enabled.

Or enable feature static-link, the crate will download and complie RocksDB automatically, including its dependencies.

cargo build --features static-link

Running

Cargo.toml

[dependencies.rocksdb]
git = "https://github.com/pingcap/rust-rocksdb.git"

Code

extern crate rocksdb;
use rocksdb::{DB, Writable};

fn main() {
    let mut db = DB::open_default("/path/for/rocksdb/storage").unwrap();
    db.put(b"my key", b"my value");
    match db.get(b"my key") {
        Ok(Some(value)) => println!("retrieved value {}", value.to_utf8().unwrap()),
        Ok(None) => println!("value not found"),
        Err(e) => println!("operational problem encountered: {}", e),
    }

    db.delete(b"my key");
}

Doing an atomic commit of several writes

extern crate rocksdb;
use rocksdb::{DB, WriteBatch, Writable};

fn main() {
    // NB: db is automatically freed at end of lifetime
    let mut db = DB::open_default("/path/for/rocksdb/storage").unwrap();
    {
        let mut batch = WriteBatch::new(); // WriteBatch and db both have trait Writable
        batch.put(b"my key", b"my value");
        batch.put(b"key2", b"value2");
        batch.put(b"key3", b"value3");
        db.write(batch); // Atomically commits the batch
    }
}

Getting an Iterator

extern crate rocksdb;
use rocksdb::{DB, Direction, IteratorMode};

fn main() {
    // NB: db is automatically freed at end of lifetime
    let mut db = DB::open_default("/path/for/rocksdb/storage").unwrap();
    let mut iter = db.iterator(IteratorMode::Start); // Always iterates forward
    for (key, value) in iter {
        println!("Saw {} {}", key, value); //actually, need to convert [u8] keys into Strings
    }
    iter = db.iterator(IteratorMode::End);  // Always iterates backward
    for (key, value) in iter {
        println!("Saw {} {}", key, value);
    }
    iter = db.iterator(IteratorMode::From(b"my key", Direction::forward)); // From a key in Direction::{forward,reverse}
    for (key, value) in iter {
        println!("Saw {} {}", key, value);
    }

    // You can seek with an existing Iterator instance, too
    iter.set_mode(IteratorMode::From(b"another key", Direction::reverse));
    for (key, value) in iter {
        println!("Saw {} {}", key, value);
    }
}

Getting an Iterator from a Snapshot

extern crate rocksdb;
use rocksdb::{DB, Direction};

fn main() {
    // NB: db is automatically freed at end of lifetime
    let mut db = DB::open_default("/path/for/rocksdb/storage").unwrap();
    let snapshot = db.snapshot(); // Creates a longer-term snapshot of the DB, but freed when goes out of scope
    let mut iter = snapshot.iterator(IteratorMode::Start); // Make as many iterators as you'd like from one snapshot
}

Rustic Merge Operator

extern crate rocksdb;
use rocksdb::{Options, DB, MergeOperands, Writable};

fn concat_merge(new_key: &[u8], existing_val: Option<&[u8]>,
    operands: &mut MergeOperands) -> Vec<u8> {
    let mut result: Vec<u8> = Vec::with_capacity(operands.size_hint().0);
    existing_val.map(|v| {
        for e in v {
            result.push(*e)
        }
    });
    for op in operands {
        for e in op {
            result.push(*e)
        }
    }
    result
}

fn main() {
    let path = "/path/to/rocksdb";
    let mut opts = Options::new();
    opts.create_if_missing(true);
    opts.add_merge_operator("test operator", concat_merge);
    let mut db = DB::open(&opts, path).unwrap();
    let p = db.put(b"k1", b"a");
    db.merge(b"k1", b"b");
    db.merge(b"k1", b"c");
    db.merge(b"k1", b"d");
    db.merge(b"k1", b"efg");
    let r = db.get(b"k1");
    assert!(r.unwrap().unwrap().to_utf8().unwrap() == "abcdefg");
}

Apply Some Tunings

Please read the official tuning guide, and most importantly, measure performance under realistic workloads with realistic hardware.

use rocksdb::{Options, DB};
use rocksdb::DBCompactionStyle::DBUniversalCompaction;

fn badly_tuned_for_somebody_elses_disk() -> DB {
    let path = "_rust_rocksdb_optimizetest";
    let mut opts = Options::new();
    opts.create_if_missing(true);
    opts.set_max_open_files(10000);
    opts.set_use_fsync(false);
    opts.set_bytes_per_sync(8388608);
    opts.set_disable_data_sync(false);
    opts.set_block_cache_size_mb(1024);
    opts.set_table_cache_num_shard_bits(6);
    opts.set_max_write_buffer_number(32);
    opts.set_write_buffer_size(536870912);
    opts.set_target_file_size_base(1073741824);
    opts.set_min_write_buffer_number_to_merge(4);
    opts.set_level_zero_stop_writes_trigger(2000);
    opts.set_level_zero_slowdown_writes_trigger(0);
    opts.set_compaction_style(DBUniversalCompaction);
    opts.set_max_background_compactions(4);
    opts.set_max_background_flushes(4);
    opts.set_disable_auto_compactions(true);

    DB::open(&opts, path).unwrap()
}