level-orm

Simple ORM built on leveldb/levelup

level-orm

Simple ORM built on leveldb/levelup.

Installation

This module is installed via npm:

$ npm install level-orm

You extend the base class to give you ORM getters and setters.

NB: You pass in a 'container' object to the Model constructor which must have a leveldb instance on the db property of the object. This allows you to share state between models by passing in the same container object for each sublevel model object that you create.

var level = require('level');
var db = level('/tmp/db', { valueEncoding: 'json' });
var Model = require('level-orm');
function Users(db) {
  // users is the sublevel name to user 
  // handle is the primary key to user for insertion 
  Models.call(this, { db: db }, 'users', 'handle');
}
util.inherits(Users, Models);
 
var users = new Users(db);
 
// save to database 
users.save({ handle: 'eugeneware', name: 'Eugene', email: 'eugene@noblesamurai.com' },
  function (errid) {
    // id will be the primary key 
  });
 
// retrieve from database 
users.get('eugeneware', function (erruser) { });
 
// delete from database 
users.del('eugeneware');
 
// stream from database 
users.createReadStream({start: 'a', end: 'c'}).pipe(...);

If you use bytewise you can have compound keys, like so:

var level = require('level');
var bytewise = require('bytewise/hex');
var db = level('/tmp/db', { keyEncoding: bytewise, valueEncoding: 'json' });
var Model = require('level-orm');
 
function Feed(db) {
  // compound key of 'user' and 'id' 
  Models.call(this, { db: db }, 'feed', ['user', 'id']);
}
util.inherits(Feed, Models);
 
var feed = new Feed(db);
feed.save({ user: 'eugeneware', id: 123, message: 'Test' }, cb);

NB: That in leveldb the default encoding is 'utf8' where keys will sort lexicographically. Thus 10 will sort before 2 unless you use an encoding such as bytewise to change this behaviour.

Implement the keyfn function on the extended model to automatically generate keys when none is found in the model to be saved:

var level = require('level');
var bytewise = require('bytewise/hex');
// we're just going to use a unique timestamp for our keys 
var timestamp = require('monotonic-timestamp');
var db = level('/tmp/db', { keyEncoding: bytewise, valueEncoding: 'json' });
function Messages(db) {
  Models.call(this, { db: db }, 'messages', 'id');
}
util.inherits(Messages, Models);
// set the function to generate ids 
Messages.prototype.keyfn = timestamp;
 
var messages = new Messages(db);
messages.save({ message: 'My message' }, function (errid) {
  // id will contain the auto-generated ID 
});
var level = require('level');
var bytewise = require('bytewise/hex');
var timestamp = require('monotonic-timestamp');
 
// Container class 
function LevelMicroBlog(dbPath) {
  this.db = sublevel(level(dbPath, { keyEncoding: bytewise, valueEncoding: 'json' }));
  this.Users = new Users(this);
  this.Messages = new Messages(this);
}
 
LevelMicroBlog.prototype.close = function(cb) {
  if (this.db) return this.db.close(cb);
  this.db = null;
  cb(null);
}
 
// Users sublevel model 
function Users(container) {
  Models.call(this, container, 'users', 'handle');
}
util.inherits(Users, Models);
 
// Messages sublevel model 
function Messages(container) {
  Models.call(this, container, 'messages', 'id');
}
util.inherits(Messages, Models);
Messages.prototype.keyfn = timestamp;
 
// instantiate a new container class 
var mblog = new LevelMicroBlog('/tmp/db');
mblog.Users.save({ 'handle': 'EugeneWare', name: 'Eugene Ware'}, ...);
mblog.Messages.save({ message: 'A new message' }, ...);

The original level-sublevel(https://github.com/dominictarr/level-sublevel) didn't support binary encodings, but as of 0.6 of sublevel, you can use native bytewise encoding of sublevels. If you want this, then require level-orm/bytewise and the underlying sublevel will use bytewise to encode sublevels:

var Model = require('level-orm/bytewise');
// extend as usual 

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