Activerecord::Crate::Adapter

The Crate adapter for ActiveRecord.

Work in progress

I've just started coding the adapter and lots of functionality might still not work. Give it a try and help bei either contributing (fix it) or add an issue.

Installation

Add this line to your application's Gemfile:

gem 'activerecord-crate-adapter', :git => "https://github.com/crate/activerecord-crate-adapter.git"

And then execute:

$ bundle

Or install it yourself as:

$ gem install activerecord-crate-adapter

Usage

When using Rails update your database.yml

 development:
   adapter: crate
   host: 127.0.0.1
   port: 4200

Crate doesn't come with an autoincrement feature for your model ids. So you need to set it yourself. One way is to use SecureRandom.uuid, if you think there is a better one, please add an issue so we can discuss.

class Post < ActiveRecord::Base

  before_validation :set_id

  private

  def set_id
    self.id = SecureRandom.uuid
  end

end

Special Data Types

Array

You can simply create Array columns by specifying t.array and passing array_type when you create a migration. You need at least the upcoming release 0.39 of Crate for this functionality.

t.array :tags, array_type: :string
t.array :votes, array_type: :integer
t.array :bool_arr, array_type: :boolean

When you create an object just pass your Array directly

Post.create!(title: 'Arrays are awesome', tags: %w(hot fresh), votes: [1,2])
post = Post.where("'fresh' = ANY (tags)")

Object

Crate allows you to define nested objects. You need at least the upcoming release 0.39 of Crate for this functionality. I tried to make it as simply as possible to use and reuse existing AR functionality, I therefore ask you to reuse the existing serialize functionality. AR#serialize allows you to define your own serialization mechanism and we simply reuse that for serializing an AR object. To get serialize working simply create a #dump and #load method on the class that creates a literal statement that is then used in the SQL. Read up more in this [commit}(https://github.com/crate/crate/commit/16a3d4b3f23996a327f91cdacef573f7ba946017).

I tried to make your guys life easier and created a module that does this automatically for you. Simply make all attributes accessible and assign it in the initializer. So a serialized class should look like this:

require 'active_record/attribute_methods/crate_object'

class Address
  attr_accessor :street, :city, :phones, :zip

  include CrateObject

  def initialize(opts)
    @street = opts[:street]
    @city = opts[:city]
    @phones = opts[:phones]
    @zip = opts[:zip]
  end

end

Check out CrateObject module if you need to write your own serializer.

Then in your model simply use #serialize to have objects working

  class User < ActiveRecord::Base        
    serialize :address, Address  
  end

Note: I do not plan to support nested objects inside objects.

Object Migrations

In the migrations you can create an object and specify the object behaviour(strict|dynamic|ignored) and it's schema.

t.object :address, object_schema_behaviour: :strict,
                   object_schema: {street: :string, city: :string, phones: {array: :string}, zip: :integer}

Migrations

Currently adding and dropping indices is not support by Crate. Issue #733

# not supported by Crate yet
add_index :posts, :comment_count
remove_index :posts, :comment_count

Gotchas

Crate is eventually consistent, that means if you create a record and query for it right away it won't work (except queries for the primary key!). Read more about it here

Crate does not support Joins (yet) so joins won't work.

Tests

First run the test instance of crate

$ ./spec/test_server.rb

then run the tests

$ rspec spec

Contributing

This adapter is a work in progress. If you think something is missing, either follow the steps below or log a new issue, so someone else can tackle it.

Fork it ( http://github.com/crate/activerecord-crate-adapter/fork )
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Add tests
Push to the branch (git push origin my-new-feature)
Create new Pull Request

Maintainer

Christoph Klocker, @corck