marsdb

MarsDB

MarsDB is a lightweight client-side database. It's based on a Meteor’s minimongo matching/modifying implementation. It's carefully written on ES6, have a Promise based interface and may be backed with any storage implementation (LevelUP, LocalStorage, IndexedDB, etc). For now implemented only LocalStorage and LocalForage storage managers. It's also supports observable cursors.

MarsDB supports any kind of find/update/remove operations that Meteor’s minimongo does. So, go to the Meteor docs for supported query/modifier operations.

You can use it in any JS environment (Browser, Electron, NW.js, Node.js).

Features

• Promise based API
• Carefully written on ES6
• Supports many of MongoDB query/modify operations – thanks to a Meteor’s minimongo
• Flexible pipeline – map, reduce, custom sorting function, filtering. All with a sexy JS interface (no ugly mongo’s aggregation language)
• Persistence API – all collections can be stored (and restored) with any kind of storage (in-memory, LocalStorage, LevelUP, etc)
• Observable queries - live queries just like in Meteor, but with simplier interface
• Reactive joins – out of the box

Examples

Using within non-ES6 environment

The ./dist folder contains already compiled to a ES5 code, but some polyfills needed. For using in a browser you must to include marsdb.polyfills.js before marsdb.min.js. In node.js you need to require(‘marsdb/polyfills’). It sets in a window/global: Promise, Set and Symbol.

Create a collection

import Collection from ‘marsdb’;
import LocalStorageManager from 'marsdb/lib/LocalStorageManager';

// Setup different id generator and storage managers
// Default storage is in-memory
Collection.defaultStorageManager(LocalStorageManager);
Collection.defaultIdGenerator(() => {
  return {
    value: Math.random(),
    seed: 0,
  };
});

const users = new Collection(‘users’);

Find a documents

const posts = new Collection(‘posts’);
posts.find({author: ‘Bob’})
  .sort([‘createdAt’])
  .then(docs => {
    // do something with docs
  });

Find with pipeline (map, reduce, filter)

An order of pipeline methods invokation is important. Next pipeline operation gives as argument a result of a previous operation.

const posts = new Collection(‘posts’);

// Get number of all comments in the DB
posts.find()
  .limit(10)
  .sortFunc((a, b) => a - b + 10)
  .filter(doc => Matsh.sqrt(doc.comment.length) > 1.5)
  .map(doc => doc.comments.length)
  .reduce((acum, val) => acum + val)
  .then(result => {
    // result is a number of all comments
    // in all found posts
  });

// Result is `undefined` because posts
// is not exists and additional processing
// is not ran (thanks to `.ifNotEmpty()`)
posts.find({author: 'not_existing_name'})
  .aggregate(docs => docs[0])
  .ifNotEmpty()
  .aggregate(user => user.name)

Find with observing changes

Observable cursor returned only by a find method of a collection. Updates of the cursor is batched and debounced (default batch size is 20 and debounce time is 1000 / 15 ms). You can change the paramters by batchSize and debounce methods of an observable cursor (methods is chained).

const posts = new Collection(‘posts’);
const stopper = posts.find({tags: {$in: [‘marsdb’, ‘is’, ‘awesome’]}})
  .observe(docs => {
    // invoked on every result change
    // (on initial result too)
    stopper.stop(); // stops observing
  }).then(docs => {
    // invoked once on initial result
    // (after `observer` callback)
  });

Find with joins

const users = new Collection(‘users’);
const posts = new Collection(‘posts’);
posts.find()
  .join(doc => {
    // Return a Promise for waiting of the result.
    return users.findOne(doc.authorId).then(user => {
      doc.authorObj = user;
      // any return is ignored
    });
  })
  .join(doc => {
    // For reactive join you must invoke `observe` instead `then`
    // That's it!
    return users.findOne(doc.authorId).observe(user => {
      doc.authorObj = user;
    });
  })
  .join((doc, updated) => {
    // Also any other “join” mutations supported
    doc.another = _cached_data_by_post[doc._id];

    // Manually update a joined parameter and propagate
    // update event from current cursor to a root
    // (`observe` callback invoked)
    setTimeout(() => {
      doc.another = 'some another user';
      updated();
    }, 10);
  })
  .observe((posts) => {
    // do something with posts with authors
    // invoked any time when posts changed
    // (and when observed joins changed too)
  })

Inserting

const posts = new Collection(‘posts’);
posts.insert({text: ‘MarsDB is awesome’}).then(docId => {
  // Invoked after persisting document
})
posts.insertAll(
  {text: ‘MarsDB’},
  {text: ‘is’},
  {text: ‘awesome’}
).then(docsIds => {
  // invoked when all documents inserted
});

Updating

const posts = new Collection(‘posts’);
posts.update(
  {authorId: {$in: [1, 2, 3]}},
  {$set: {text: ‘noop’}}
).then(result => {
  console.log(result.modified) // count of modified docs
  console.log(result.updated) // array of updated docs
  console.log(result.original) // array of original docs
});

Removing

const posts = new Collection(‘posts’);
posts.remove({authorId: {$in: [1,2,3]}})
  .then(removedDocs => {
    // do something with removed documents array
  });

Roadmap

• Keep track of multiple remove/update documents in selector (allow only if opations.multi passed)
• Upsert updating
• Indexes support for some kind of simple requests {a: '^b'}, {a: {$lt: 9}}
• Some set of backends
• Documentation

Contributing

I’m waiting for your pull requests and issues. Don’t forget to execute gulp lint before requesting. Accepted only requests without errors.

License

See License