Updraft

Updraft is an asynchronous Javascript object-relational mapping (ORM)-like library, very similar to persistence.js. It can work in the browser, on a server using node.js, or in a Cordova app using the SQLitePlugin (basically, anywhere WebSQL or a SQLlite interface is supported). It does not support MySQL, in-memory, local storage, or IndexedDB.

Status

Updraft has not yet been used in any project and is still under heavy development. Expect bugs. You shouldn't use it if you know nothing about SQL.

Sync is planned but not implemented.

Motivations

• Automatic schema migration (within reason)
• Syncing with cloud-based databases, like Dropbox's Sync API or iCloud's CloudKit
• Modern best practices- asynchronous programming using Promises, Test-driven development, Code coverage

Change history

Most databases store only the latest records, which works well when there is only one database. Once you start syncing between multiple databases, you start running into problems. How do you merge records? What if one user deleted a record that another modified?

Updraft addresses these problems by storing baseline records and changes. Users can insert a baseline (that is, whole) record at any time, but this is intended to be done only once, because only the latest record is considered the baseline. Subsequent modifications should be made as deltas- you tell the database to made a change, and it applies the delta to the latest record, as well as keeping a record of all deltas and their timestamp. Every time a change comes in, it runs all the deltas in order and updates the latest record.

This system makes conflict resolution trivial- if two users change the same record offline, once they resume syncing their changes will automatically merge based on the time they came in.

Deltas

Deltas are based on React's immutability helpers, which in turn is based on MongoDB's query language, though there is no tie to any database. They are immutable operations, meaning they leave the source object untouched.
For example:

var record = {
  id: 123,
  text: "original text"
};

var delta = {
  text: { $set: "new text" }
};

var newRecord = Updraft.update(record, delta);
// record -> { id: 123, text: "original text" }
// newRecord -> { id: 123, text: "new text" }

Important differences from other ORM frameworks

You should think of Updraft as more of a wrapper over executing SQL statements yourself, rather than a complete ORM framework. Objects won't be cached or saved unless you do it yourself. You will have to define your primary key (only one is supported) as well as create and assign a unique value for that key.

You also won't find one-to-one or many-to-many or other SQL-centric ideas. You can define a field of type 'set' where you can have a (homogeneous) set of values or object keys. You will be responsible for tracking object lifetimes and deleting any orphaned entities.

Dependencies

You need a JS environment that supports Promises or you can use a library like lie.

Though written in TypeScript, it will run in any JS environment (browser, node.js)

Installation

npm:

npm install --save updraft

Bower:

bower install --save updraft

Usage

Basic usage is as follows:

var taskSpec = {
  name: 'tasks',
  columns: {
    id: Updraft.Column.Text().Key(),
    description: Updraft.Column.Text(),
    done: Updraft.Column.Bool()
  }
};

var sqlite3 = require("sqlite3");
var db = new sqlite3.Database("test.db");

var store = new Updraft.createStore({ db: Updraft.createSQLiteWrapper(db) });
var taskTable = store.createTable(taskSpec);
var time = Date.now();

store.open({name: 'my database'})
  .then(function() {

    var task = {
      id: 123,
      description: "task description",
      done: false
    };

    // save baseline
    return taskTable.add([{ time: time, create: task }]);
  })
  .then(function() {

    var delta = {
      description: { $set: "changed description" },
      done: { $set: true }
    };
    
    // in a real application you would just use Date.now(), since it's probably not the
    // same second you created the record
    time = time + 1;

    // save the change
    return taskTable.add([{ time: time, delta: delta }]);
  })
  .then(function() {
    // find the value with id 123.  See docs for more advanced query options
    return taskTable.find({id: 123});
  })
  .then(function(results) {
    var task = results[0];
    // -> { id: 123, description: "changed description" }
  })
  ;

If you use TypeScript, you can use interfaces to make your life easier and let the compiler catch errors:

import D = Updraft.Delta;
import Q = Updraft.Query;

// either set up multiple interfaces for declarations and queries:
interface Task {
  id: number;
  description: string;
  done: boolean; 
}

interface TaskDelta {
  id: number; // NOTE: database does not support changing the key value
  description: D.str;
  done: D.bool;
}

interface TaskQuery {
  id: Q.num;
  description: Q.str;
  done: Q.bool;
}

// or use templates to keep things [DRY](https://en.wikipedia.org/wiki/Don%27t_repeat_yourself)
interface _Task<key, str, bool> {
  id: key;
  description: str;
  done: bool;
}

interface Task extends _Task<number, string, boolean> {}
interface TaskDelta extends _Task<number, D.str, D.bool> {}
interface TaskQuery extends _Task<Q.num, Q.str, Q.bool> {}

// then set up your table
type TaskTable = Updraft.Table<Task, TaskDelta, TaskQuery>;
type TaskTableSpec = Updraft.TableSpec<Task, TaskDelta, TaskQuery>;

const taskSpec: TaskTableSpec = {
  name: 'tasks',
  columns: {
    id: Updraft.Column.Text().Key(),
    description: Updraft.Column.Text(),
    done: Updraft.Column.Bool()
  }
};

// ...

var store = new Updraft.createStore({ db: Updraft.createSQLiteWrapper(db) });
var taskTable: TaskTable = store.createTable(taskSpec);

For advanced usage, see the documentation.

Enums

Updraft supports typescript enums and enum-like objects, such as those created using the enum library, with no dependency on any specific library. They will be saved as the object's 'toString()' value and restored using the class's 'get(value)' method. They are stored in the db as strings.

var store = new Updraft.createStore(/* ... */);

var ColorTemperature = new Enum({'Cool', 'Neutral', 'Warm'});

var paintTable = store.createClass({
  tableName: 'paints',
  columns: {
    name: Updraft.Column.Text().Key(),
    colorTemp: Updraft.Column.Enum(ColorTemperature)
  }
});

var paint = {
  name: "cyan",
  colorTemp: ColorTemperature.Cool,
};

// ...

paintTable.find({ colorTemp: ColorTemperature.Cool }).then(/* ... */);

Schemas and Migration

For most simple changes, Updraft will have you covered. You can feel free to add a new field, a new class, remove fields or classes, add or remove indices, and rename fields without needing to do any extra work. You can also change field types, but because the underlying database is SQLite, the 'type' is only a column affinity- no schema change/migration will happen; you can always store any type (int/string/blob/etc) in any field.

During migrations, removed and renamed columns will be preserved not only in the resulting table but also by walking every change and updating the delta objects. Because of this, it might take some time depending on how many records you have.

Not supported:

• changing the primary key
• changing table names
• multi-column primary keys

Documentation

There is auto-generated documentation in doc/index.html

For examples see the test folder

Contributing

We'll check out your contribution if you:

• Provide a comprehensive suite of tests for your fork.
• Have a clear and documented rationale for your changes.
• Package these up in a pull request.

We'll do our best to help you out with any contribution issues you may have.

License

MIT. See LICENSE.txt in this directory.