About
The Ruby on Rails ActiveRecord adapter for CrateDB, using the crate_ruby driver with HTTP connectivity.
Note: The activerecord-crate-adapter currently only works with Rails 4.1.x.
Installation
Add this line to your application's Gemfile:
gem 'activerecord-crate-adapter'
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
CrateDB 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, on: :create
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.
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
CrateDB allows you to define nested objects. 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 #dump and #load methods
on the class that creates a literal statement that is then used in the SQL. Read up more in this commit about array and object literals.
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 the 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, specify the object behaviour
(strict|dynamic|ignored), and its 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 CrateDB, see issue #733.
# not supported by CrateDB yet
add_index :posts, :comment_count
remove_index :posts, :comment_count
Caveats
CrateDB 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).
In this context, read more about the REFRESH TABLE statement.
Tests
See DEVELOP.md.
Contributing
If you think something is missing, either create a pull request or log a new issue, so someone else can tackle it. Please refer to CONTRIBUTING.rst for further information.
Maintainers
License
This project is licensed under the Apache License 2.0.