Cequel Migrations Rails Plugin

This Rails plugin basically provides a migration setup very similar to the standard ActiveRecord based migration system that normally exists in rails. The BIG difference is that it is designed to support specifically migrations for Cassandra data stores using Cequel.

Installation

Add this line to your application's Gemfile:

gem 'cequel-migrations-rails'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cequel-migrations-rails

Usage

For information on how to use this gem in your rails app please refer to the following. Note: You need to have the cequel gem setup and configured already in your Rails app before using this gem.

Initial Setup

Before you can start using this gem you need to create the initial directory structure in your Rails app for it. You can do this using the following command:

rails g cequel:migrations:install

This creates the directory structure cequel/migrate/ at the root of your Rails application as the place to store your migration scripts.

Generate Migration File

To write a migration you first need to generate a migration file. This is done with the following command where <migration_name> is replaced with the name of the migration.

rails g cequel:migration <migration_name>

An example of the above command with a migration name would look as follows:

rails g cequel:migration CreateUserColumnFamily

Create Database

To create the database specified in your config/cequel.yml and create a column family in it called schema_migrations run the following command:

rake cequel:create

Strategy & Strategy Options

Before cequel:create will work the strategy_class and any strategy_options need to be set per environment in the config/cequel.yml config as seen in the example below.

development:
  host: '127.0.0.1:9160'
  keyspace: capture_api_dev
  strategy_class: SimpleStrategy
  strategy_options:
    replication_factor: 1

Drop Database

If you have already created the database and you want to drop it to start from scratch or something you can do so by running the following command:

rake cequel:drop

Migrate Database

If you database exists with a schema_migrations column family already because you followed the directions above in the "Create Database" section you can migrate the database with the following command:

rake cequel:migrate

Rollback Migrations

If you need to rollback a migration you do so with the following command:

rake cequel:rollback

If you need to rollback multiple migrations you can do so as follows, where 5 is the number of steps I wanted to rollback.

STEPS=5 rake cequel:rollback

Writing Migrations

When you generate a migration you may know that it sets up the migration class with a base class of Cequel::Migration.

The Cequel::Migration class provides the execute method to be used inside of your migrations up and down methods. The execute method takes a string of CQL.

At the moment we currently only provide the execute method. However, we plan to provide other helper functions like, create_column_family, drop_column_family, etc.

Example Migration

Below is an example migration which creates a column family in the up method and drops the column family in the down method. Here we can see that the migration inherits from the Cequel::Migrations and see that we are using the execute method to execute CQL strings within the up and down methods as describe above.

The migration exists at the following path, cequel/migrate/20121130082818_create_visitor_events_column_family.rb relative to the project root directory.

class CreateVisitorEventsColumnFamily < Cequel::Migration
  def up
    execute("CREATE COLUMNFAMILY visitor_events (visitor_id uuid PRIMARY KEY)")
  end

  def down
    execute("DROP COLUMNFAMILY visitor_events")
  end
end

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request