Compression

Bit Packing / Mostly Encoding

FineDB makes use of Google's Snappy (previously known as Zippy), which is open-source and written in C++. Snappy uses byte-oriented encoding during the compression process.

Concurrency Control

Multi-version Concurrency Control (MVCC)

Again, since FineDB is derived from LMDB, we see that the concurrency control other than that of the system as a whole is directly handled by the LMDB storage engine. Thus, we has the use of MVCC so that readers and writers do not block each other.

Data Model

Key/Value

After compression, data is stored in a key with a description (1 byte), replication timestamp (8 bytes), expiration time stamp (8 bytes), and the data (n bytes). The length of the key is 64KB and length of the data is 4GB.

Foreign Keys

Not Supported

Indexes

B+Tree

Since this system is derived from LMDB, the indexing uses that of LMDB. The DB uses 2 B+ trees to maintain the data pages and the free pages. The performance is heavily reliant on the length o the transactions.

Joins

Not Supported

Query Compilation

Not Supported

Query Interface

Custom API

The server uses a binary protocol to communicate with the client. The requests contain a byte describing the command and is followed by other data if the request requires it. The response follows a similar format.

Storage Architecture

In-Memory

Since the DB uses LMDB as the storage model, we look at LMDB's architecture and see that it is in memory and uses mmap. Since it uses mmap, the actual memory is bounded and is controlled by the OS.

Storage Model

Custom

Stored Procedures

Not Supported

System Architecture

Shared-Everything

There are three main types of threads in the server. The main thread creates the other threads while listening for connections. The write thread writes into the LMDB storage engine asynchronously. The communication threads read in the requests and communicate with the client-side.

Views

Not Supported