Nodejs + LevelDB Talk

talk.md

Intro into level db

https://code.google.com/p/leveldb/

• It's a database, it's by google, and is what supports IndexDB in the chrome browser
• It's also been used to store data in riak
• It lives in your process (a bit like sqlite)
• Inspired by Big Table, but designed to work on mobile devices
• There is great support for leveldb in the node.js
• Node is a great tool for sticking technologies together
• This is driving a new database ecosystem, and way of creating a modular database

$ mkdir talk
$ cd talk
$ sudo npm install level

$ node

> var level = require('level');
> var db = level('db');

> db.put('hello', 'norwich');
> db.put('goodbye', 'cruel world');

> db.get('hello', console.log);

> db.put('d', 'true')
> db.put('c', 'true')
> db.put('b', 'true')
> db.put('a', 'true')

> var x = db.readStream()
> x.on('data', console.log)

// this is a sorted key list

> var x = db.readStream({start:'b', end:'d'}).on('data', console.log);

// you can sort sub-ranges, and in reverse

> var x = db.readStream({start:'b', end:'d', reverse:true}).on('data', console.log);

There is a also a batch insert mode

Level-sub level

Databases don't normally contain just one kind of data, you want to mix types together. We can use level-sublevel for this.

$ sudo npm install level-sublevel
$ node

> var db = require('level')('db');
> var sublevel = require('level-sublevel')(db);
> var stuffdb = sublevel.sublevel('stuff');
> stuffdb.put('foo', 'bar')l
> var _ = stuffdb.readStream().on('data', console.log);

// what's going on?

> var _ = sublevel.readStream().on('data', console.log);
> var _ = db.readStream().on('data', console.log);

// it's better to use sub-key ranges than having multiple databases

http

$ sudo npm install express
$ nano server.js

var app = require('express')();
var db = require('level')('db');

app.get("/:key", function(req, res){
  db.get(req.params.key, function(err, data){
    res.json({value: data});
  });
});

app.get("/", function(req, res){
  var results = [];
  db.readStream().on('data', function(data){
    results.push(data);
  })
  .on('end', function(){
    res.json(results);
  });
});

app.listen(8080);

$ node server

lev

lev is a command line tool to inspect your database

$ npm install lev -g
$ lev db

> ls
> get hello
> cd stuff
> ls

level-geospatial

$ npm install level-geospatial
$ node load
$ less uk-postcodes.csv
$ less load.js

> var db = require('level')('geo');
> var geo = require('level-geospatial')(db)
> var _= geo.search({lat:52.6, lon: 1.3}, 10000).on('data', console.log)
> geo.put({lat:52.6, lon:1.3}, 'nordevcon', 'hello world')
> var _= geo.search({lat:52.6, lon: 1.3}, 10000).on('data', console.log)

Other places to look

• levelgraph

A graph database (triplestore) built on leveldb

https://www.npmjs.org/package/levelgraph

• azureleveldown

An implementation of LevelDown for Windows Azure Table Storage

https://www.npmjs.org/package/azureleveldown

• LevelUp Wiki

A more complete list of leveldb modules

https://github.com/rvagg/node-levelup/wiki/Modules