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    driver.rb migration.rb persistence.rb rake_migration.rb spec.rb

  • migration.rb

  • ¶

    Example of Data Migration for [MongoDB Enhanced Driver][mongodb].

    In this example we'll define two migrations, applying first one, rollback it, and then migrating database to the latest version.

    Usually all this is [done via Rake Task][rake_migration], but in this example we do it by hand.

    Requiring support for migration.

    require 'mongo/migration'
  • ¶

    Defining first migration, creating Zeratul (and removing it in rollback).

    Mongo.migration 1 do |m|
  m.up  {|db| db.units.save   name: 'Zeratul'}
  m.down{|db| db.units.remove name: 'Zeratul'}
end
  • ¶

    Defining second migration, creating Tassadar (and removing it in rollback).

    Mongo.migration 2 do |m|
  m.up  {|db| db.units.save   name: 'Tassadar'}
  m.down{|db| db.units.remove name: 'Tassadar'}
end
  • ¶

    Connecting to test database and cleaning it before starting the sample.

    connection = Mongo::Connection.new
db = connection.default_test
db.drop
  • ¶

    Assigning database to migration.

    Mongo.migration.db = db
  • ¶

    Let's migrate to the first version and create mighty Zeratul.

    Mongo.migration.update 1

p Mongo.migration.current_version                # => 1
p db.units.all                                   # => [Zeratul]
  • ¶

    Rolling it back.

    Mongo.migration.update 0

p Mongo.migration.current_version                # => 0
p db.units.all                                   # => []
  • ¶

    Updating to the latest version (if there's no explicit version then the highest available version will be chosen).

    Mongo.migration.update

p Mongo.migration.current_version                # => 2
p db.units.all                                   # => [Zeratul, Tassadar]
  • ¶