README.md

LSMDB

A database implementation based on simplified LSM tree(Log-structured Merge Tree)

Project of SE-2322 Advanced data structure

Getting Started

I use CMake to compile all the tests and main entry(src/main.cpp).

Three tests(compaction, correctness, persistence) are in the tests directory.

The main entry is like a playground and you can create a LSMDB(aka. KVStore) object, specify the data path and play with it.

Features

support basic Database operations —— CRUD

1. PUT

   void KVStore::put(uint64_t key, const std::string value);

2. GET

   std::string KVStore::get(uint64_t key);

3. DELETE

   bool del(uint64_t key);

4. RESTART

   After restart, it will first scan the ./data directory to build SSTable from existing files.

Performance

Check LSM_Tree实验报告 for a detailed and vivid report.

Storage Structure

memory

1. memtable.
2. SSTable except the value part.

disk

Level n 层的文件数量上限为 $2^{n+1}$（即Level 0 是 2，Level 1 是 4，Level 2 是 8，……）

除了 Level 0 之外，每一层中各个文件的键值区间不相交。

./data
	|__level-0
		|__ 0.sst
		|__ 1.sst
	|__level-1
		|__ 0.sst
		|__ 1.sst
		|__ 2.sst
		|__ 3.sst
	|_level-2
	...