History[03]

It has released two main versions (v1.8 and v2.0), while v3.0 is still work in progress.

Checkpoints[05][06]

It does not fully support no redo log and recovery. nessDB v3.0 will support sharp checkpoint with a 60 seconds period according to the code, but the recovery part has not been finished.

Compression[07][08]

nessDB v3.0 used Snappy, a data compression and decompression library written in C++ by Google, to compress the buffered-tree node data when serializing the node to disk and decompress it when deserializing. nessDB v2.0 used QuickLZ, a compression library written in C, to compress the key-value pair.

Concurrency Control[09][10][11]

nessDB v3.0 will use two-phase locking with deadlock detection, but this part does not finish yet. For deadlock detection, nessDB v3.0 will use Helgrind, a thread error detector that can detect potential deadlocks arising from lock ordering problems.

For nessDB v2.0, it is a single-thread engine. The engine can process a single request at a time.

Data Model[12][13][14]

nessDB is a key-value DBMS, which supports Redis-like protocol, such as SET, GET, DEL, EXISTS. To be specific, both key and value are general raw data and are represented by a pointer with length.

Foreign Keys

nessDB is a key-value DBMS so it does not support foreign key.

Indexes[03][04]

nessDB used LSM-tree (Log-Structured Merge Tree) in v1.8, Small-Splittable Tree in v2.0, and will use fractal-tree in v3.0 for key-value storage. Those data structures are suitable for high-performance insertion compared to B-tree.

Isolation Levels[15]

nessDB v3.0 support four isolation levels: read uncommitted, read committed, repeatable read and serializable.

Joins[12]

nessDB does not support join. It is a key-value DBMS with only interfaces such as SET, GET, DEL, EXISTS.

Storage Architecture

Storage Model

System Architecture