Transfer Gem

Transfer data from source database to ActiveRecord, SequelModel or Mongoid models.

Installation

Include Transfer in Gemfile:

gem 'transfer'

You can run bundle from command line:

bundle install

Compatibility

Source database: all, supported by Sequel.

Destination: ActiveRecord, SequelModel, Mongoid.

Configure

Set connection options of source database and global parameters:

Transfer.configure do |c|
  c.host = "localhost"
  c.adapter = "postgres"
  c.database = "source_database"
  c.user = "username"
  c.password = "password"
end

Available options:

• validate on/off model validations. Values: true or false, default is false.
• failure_strategy sets strategy if save of model is not successfully. Values: :ignore or :rollback, defult is :ignore.
• before global callback.
• success global callback.
• failure global callback.
• after global callback.
• another options interpreted as Sequel database connection options.

Usage

Direct transfer from source table :users to User model. All columns, including protected, existing in source table and destination model, will transferred:

transfer :users => User

Filling the field country a constant value:

transfer :users => User do
  country "England"
end

Transfer :name column from source table :users into first_name of User model:

transfer :users => User do
  first_name :name
end

To produce, dynamic value (e.g. dist_name field), you can pass a block and access the row of source table:

transfer :users => User do
  dist_name {|row| "Mr. #{row[:first_name]}"}
end

Global callbacks

This callbacks called for each transfer.

Transfer.configure do |c|
  c.before do |klass, dataset|
    #...
  end
  c.success do |model, row|
    #...
  end
  c.failure do |model, row, exception|
    #...
  end
  c.after do |klass, dataset|
    #...
  end
end

Available global callbacks:

• before called before an transfer started. Parameters: klass, dataset.
• success called if save model is successfully. Parameters: model, row.
• failure called if save model is not successfully. Parameters: row, exception.
• after called after an transfer finished. Parameters: klass, dataset.

Description of parameters:

• dataset source table dataset, instance of Sequel::Dataset.
• klass is destination class.
• model builded model, instance of klass.
• row of source table. Type: Hash.
• exception if save of model is not successfull.

Local transfer callbacks

You can specify callbacks in your transfer that are separate from the model callbacks. This callbacks called in model context, therefore self keyword points to model.

transfer :users => User do
  before_save do |row|
    self.messages << Message.build(:title => "Transfer", :description => "Welcome to new site, #{row[:fname]}!")
  end
end

Available callbacks:

• before_save called before save model. Paramaters: row.
• after_save called after successfully save model. Parameters: row.

where row is row of source table, type: Hash.

Filter columns

only filter passes source columns, specified in parameters.

transfer :users => User do
  only :name
end

except filter passes all source columns, except for those that are specified in the parameters:

transfer :users => User do
  except :name
end

Replace global options

Global options can be replaced global options, if it passed to transfer.

transfer :users => User, :validate => false, :failure_strategy => :rollback

Available options for replace:

• validate
• failure_strategy

Logging

If you also want see progress of transfer in console, use e.g. progressbar gem with global callbacks.

require 'progressbar'

Transfer.configure do |c|
  c.before {|klass, dataset| @pbar = ProgressBar.new(klass, dataset.count) }
  c.success { @pbar.inc }
  c.after { @pbar.halt }
end

transfer :users => User