canaldb's Introduction

Canaldb

A deadly simple time series databese which uses Leveldb as a backend.

Idea & Motivation

Avoid storing a value which is duplicate of the most recent value

To save storage capacity.

e.g.

Timestamp	Value	Note
1473320409401	foo	Store (original value)
1473320409402	foo	Not store (duplicated)
1473320409403	bar	Store (value chaneged)

Trimmable (truncatable) old value with according to timestamp

To truncate old data, to save storage capacity :)

e.g.

namespace and timestamp	Value
ns_1473320409401	foo
ns_1473320409402	bar
ns_1473320409403	buz
ns_1473320409410	qux

Then execute Trim()

db.Trim("ns", int64(1473320409405)) // <= timestamp is between `buz` value and `qux` value

Result:

namespace and timestamp	Value	Note
ns_1473320409405	buz	Truncate and put the latest value on boundary
ns_1473320409410	qux	As it is

Example

import "github.com/syndtr/goleveldb/leveldb"

func main() {
	leveldb, _ := leveldb.OpenFile("db", nil)
	defer leveldb.Close()
	db := NewCanalDB(leveldb)

	entry1, _ := db.Put("namespace", "1")
	entry2, _ := db.Put("namespace", "2")
	entry3, _ := db.Put("namespace", "3")

	db.GetCurrent("namespace") // => namespace:3

	db.GetRange("namespace", entry1.Timestamp, entry3.Timestamp, -1, false) // => namespace:1, namespace:2, namespace:3
	db.GetRange("namespace", entry1.Timestamp, entry3.Timestamp, -1, true)  // => namespace:3, namespace:2, namespace:1
	db.GetRange("namespace", entry1.Timestamp, entry3.Timestamp, 1, false)  // => namespace:1
	db.GetRange("namespace", entry2.Timestamp, entry3.Timestamp, -1, false) // => namespace:2, namespace:3

	db.Trim("namespace", entry3.Timestamp) // => Trim db
	db.GetRange("namespace", entry1.Timestamp, entry3.Timestamp, -1, false) // => namespace:3
}