value store written in pure Go in less than 1000 lines for learning purposes. (original) (raw)

LibraDB

LibraDB is a simple, persistent key/value store written in pure Go. The project aims to provide a working yet simple example of a working database. If you're interested in databases, I encourage you to start here.

This database accompanies my blog post on how to write a database from scratch.

Installing

To start using LibraDB, install Go and run go get:

go get -u github.com/amit-davidson/LibraDB

Basic usage

package main

import "github.com/amit-davidson/LibraDB"

func main() { path := "libra.db" db, _ := LibraDB.Open(path, LibraDB.DefaultOptions)

tx := db.WriteTx()
name := []byte("test")
collection, _ := tx.CreateCollection(name)

key, value := []byte("key1"), []byte("value1")
_ = collection.Put(key, value)

_ = tx.Commit()

}

Transactions

Read-only and read-write transactions are supported. LibraDB allows multiple read transactions or one read-write transaction at the same time. Transactions are goroutine-safe.

LibraDB has an isolation level: Serializable. In simpler words, transactions are executed one after another and not at the same time.This is the highest isolation level.

Read-write transactions

tx := db.WriteTx() ... if err := tx.Commit(); err != nil { return err }

Read-only transactions

tx := db.ReadTx() ... if err := tx.Commit(); err != nil { return err }

Collections

Collections are a grouping of key-value pairs. Collections are used to organize and quickly access data as each collection is B-Tree by itself. All keys in a collection must be unique.

tx := db.WriteTx() collection, err := tx.CreateCollection([]byte("test")) if err != nil { return err } _ = tx.Commit()

Auto generating ID

The Collection.ID() function returns an integer to be used as a unique identifier for key/value pairs.

tx := db.WriteTx() collection, err := tx.GetCollection([]byte("test")) if err != nil { return err } id := collection.ID() _ = tx.Commit()

Key-Value Pairs

Key/value pairs reside inside collections. CRUD operations are possible using the methods Collection.Put Collection.Find Collection.Remove as shown below.

tx := db.WriteTx() collection, err := tx.GetCollection([]byte("test")) if err != nil { return err }

key, value := []byte("key1"), []byte("value1") if err := collection.Put(key, value); err != nil { return err } if item, err := collection.Find(key); err != nil { return err }

if err := collection.Remove(key); err != nil { return err } _ = tx.Commit()