LSM Tree demo project

API

Set

curl -v -XPOST http://localhost:8080/api/v1/set/:key -d 'value'

Get

curl -v http://localhost:8080/api/v1/get/:key

Flush

curl -v http://localhost:8080/api/v1/flush

flush memory data to disk table and delete wal log.

Structure

set flow

1. command -> memory SSTable -> WAL
2. memory SSTable -> swich SSTable to immutable
3. flush immutable to sdb
4. delete WAL

query flow

1. query -> memory SSTable -> active SSTable -> immutable SSTable -> sparse Index -> sdb file

sdb file (SSTable)

N		N	N	40
blockLength, blockData	...	blockLength, blockData	sparse index	metainfo

spare index data

4	4	N
index.start	keyLength	index.key

meata info data

8	8	8	8	2	2	4
dataStart	dataLength	indexStart	indexLength	blockKeyNum	tableBlockNum	version

block data && wal file

4	N	4	N		4	N
commandLength	command	commandLength	command	...	commandLength	command

command data

1	4	N	4	N
commandType	keyLength	key	valueLength	value

1. block data use LZ4 compressed
2. wal log is not compressed

feature

1. memory SSTable
2. disk SSTable
3. WAL
4. memory flush to disk
5. memory SSTable use skiplist
6. L0 data has repeat key, need read latest key
7. disk SSTable compaction: Tiering compaction / Leveling compaction
8. use bitmap to improve performance