Migrate

Abstract migration framework for node.

Installation

$ npm install migrate

Usage

Usage: migrate [options] [command]

Options:

  -V, --version  output the version number
  -h, --help     output usage information

Commands:

  init           Initalize the migrations tool in a project
  list           List migrations and their status
  create <name>  Create a new migration
  up [name]      Migrate up to a given migration
  down [name]    Migrate down to a given migration
  help [cmd]     display help for [cmd]

For help with the individual commands, see migrate help [cmd]. Each command has some helpful flags for customising the behavior of the tool.

Programmatic usage

var migrate = require('migrate')

migrate.load({
  stateStore: '.migrate'
}, function (err, set) {
  if (err) {
    throw err
  }
  set.up(function (err) {
    if (err) {
      throw err
    }
    console.log('migrations successfully ran')
  })
})

Creating Migrations

To create a migration, execute migrate create <title> with a title. By default, a file in ./migrations/ will be created with the following content:

'use strict'

module.exports.up = function (next) {
  next()
}

module.exports.down = function (next) {
  next()
}

All you have to do is populate these, invoking next() when complete (no need to call next() if up/down functions are async), and you are ready to migrate!

For example:

$ migrate create add-pets
$ migrate create add-owners

The first call creates ./migrations/{timestamp in milliseconds}-add-pets.js, which we can populate:

// db is just an object shared between the migrations
var db = require('./db');

exports.up = function (next) {
  db.pets = [];
  db.pets.push('tobi')
  db.pets.push('loki')
  db.pets.push('jane')
  next()
}

exports.down = function (next) {
  db.pets.pop('pets')
  db.pets.pop('pets')
  db.pets.pop('pets')
  delete db.pets
  next()
}

The second creates ./migrations/{timestamp in milliseconds}-add-owners.js, which we can populate:

var db = require('./db');

exports.up = function (next) {
  db.owners = [];
  db.owners.push('taylor')
  db.owners.push('tj', next)
}

exports.down = function (next) {
  db.owners.pop()
  db.owners.pop()
  delete db.owners
  next()
}

Advanced migration creation

When creating migrations you have a bunch of other options to help you control how the migrations are created. You can fully configure the way the migration is made with a generator, which is just a function exported as a node module. A good example of a generator is the default one shipped with this package.

The create command accepts a flag for pointing the tool at a generator, for example:

$ migrate create --generator ./my-migrate-generator.js

A more simple and common thing you might want is to just change the default template file which is created. To do this, you can simply pass the template-file flag:

$ migrate create --template-file ./my-migration-template.js

Lastly, if you want to use newer ECMAscript features, or language addons like TypeScript, for your migrations, you can use the compiler flag. For example, to use babel with your migrations, you can do the following:

$ npm install --save babel-register
$ migrate create --compiler="js:babel-register" foo
$ migrate up --compiler="js:babel-register"

Running Migrations

When first running the migrations, all will be executed in sequence.

$ migrate
  up : migrations/1316027432511-add-pets.js
  up : migrations/1316027432512-add-jane.js
  up : migrations/1316027432575-add-owners.js
  up : migrations/1316027433425-coolest-pet.js
  migration : complete

Subsequent attempts will simply output "complete", as they have already been executed. migrate knows this because it stores the current state in ./.migrate which is typically a file that SCMs like GIT should ignore.

$ migrate
  migration : complete

If we were to create another migration using migrate create, and then execute migrations again, we would execute only those not previously executed:

$ migrate
  up : migrates/1316027433455-coolest-owner.js

You can also run migrations incrementally by specifying a migration.

$ migrate up 1316027433425-coolest-pet.js
  up : migrations/1316027432511-add-pets.js
  up : migrations/1316027432512-add-jane.js
  up : migrations/1316027432575-add-owners.js
  up : migrations/1316027433425-coolest-pet.js
  migration : complete

This will run up-migrations up to (and including) 1316027433425-coolest-pet.js. Similarly you can run down-migrations up to (and including) a specific migration, instead of migrating all the way down.

$ migrate down 1316027432512-add-jane.js
  down : migrations/1316027432575-add-owners.js
  down : migrations/1316027432512-add-jane.js
  migration : complete

Any time you want to see the current state of the migrations, you can run migrate list to see an output like:

$ migrate list
  1316027432511-add-pets.js [2017-09-23] : <No Description>
  1316027432512-add-jane.js [2017-09-23] : <No Description>

The description can be added by exporting a description field from the migration file.

Custom State Storage

By default, migrate stores the state of the migrations which have been run in a file (.migrate). But you can provide a custom storage engine if you would like to do something different, like storing them in your database of choice. A storage engine has a simple interface of load(fn) and save(set, fn). As long as what goes in as set comes out the same on load, then you are good to go!

If you are using the provided cli, you can specify the store implementation with the --store flag, which should be a require-able node module. For example:

$ migrate up --store="my-migration-store"

API

migrate.load(opts, cb)

Calls the callback with a Set based on the options passed. Options:

• set: A set instance if you created your own
• stateStore: A store instance to load and store migration state, or a string which is a path to the migration state file
• migrationsDirectory: The path to the migrations directory
• filterFunction: A filter function which will be called for each file found in the migrations directory
• sortFunction: A sort function to ensure migration order

Set.up([migration, ]cb)

Migrates up to the specified migration or, if none is specified, to the latest migration. Calls the callback cb, possibly with an error err, when done.

Set.down([migration, ]cb)

Migrates down to the specified migration or, if none is specified, to the first migration. Calls the callback cb, possibly with an error err, when done.