CassandraStore is a fun to use ORM for Cassandra with a chainable, ActiveRecord like DSL for querying, inserting, updating and deleting records plus built-in migration and keyspace management support. It is built on-top of the cassandra-driver gem, using its built-in automated paging what is drastically reducing the complexity of the code base.

Add this line to your application's Gemfile:

gem 'cassandra_store'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cassandra_store

First and foremost, you need to connect to your cassandra cluster like so:

CassandraStore::Base.configure(
  hosts: ["127.0.0.1"],
  keyspace: "my_keyspace",
  cluster_settings: { consistency: :quorum }
)

When using rails, you want to do that in an initializer. If you do not yet have a keyspace, you additionally want to pass replication settings:

CassandraStore::Base.configure(
  hosts: ["127.0.0.1"],
  keyspace: "my_keyspace",
  cluster_settings: { consistency: :quorum },
  replication: { class: 'SimpleStrategy', replication_factor: 1 }
)

Afterwards, you can create/drop the specified keyspace:

rake cassandra:keyspace:create
rake cassandra:keyspace:drop

If you are on rails and you don't have any tables yet, you can add migrations now. There is no generator yet, so you have to create them manually:

# cassandra/migrate/1589896040_create_posts.rb

class CreatePosts < CassandraStore::Migration
  def up
    execute <<-CQL
      CREATE TABLE posts (
        user TEXT,
        domain TEXT,
        id TIMEUUID,
        message TEXT,
        PRIMARY KEY ((user, domain), id)
      )
    CQL
  end

  def down
    execute "DROP TABLE posts"
  end
end

Afterwards, simply run rake cassandra:migrate.

Creating models couldn't be easier:

class Post < CassandraStore::Base
  column :user, :text, partition_key: true
  column :domain, :text, partition_key: true
  column :id, :timeuuid, clustering_key: true
  column :message, :text

  validates_presence_of :user, :domain, :message

  before_create do
    self.id ||= generate_timeuuid
  end
end

Let's check this out in detail:

  column :user, :text, partition_key: true
  column :domain, :text, partition_key: true

tells CassandraStore that your partition key is comprised of the user column as well as the domain column. For more information regarding partition keys and the data model of cassandra, please check out the cassandra docs. Afterwards, the clustering/sorting key is specified via:

column :id, :timeuuid, clustering_key: true

The id is assigned here:

  self.id ||= generate_timeuuid

Please note, CassandraStore never auto-assigns any values for you, but you have to assign them. You can pass a timestamp to generate_timeuuid as well:

  generate_timeuuid(Time.now)

This is desirable when you have timestamp columns as well and you want them to match with your timeuuid key.

Similarly, when using UUID instead of TIMEUUID you have to use generate_uuid instead.

In addition, you can of course use all kinds of validations, hooks, etc.

The interface for dealing with records and querying them is very similar to the interface of ActiveRecord:

Post.create!(user: "mrkamel", ...)
Post.create(...)
Post.new(...).save
Post.new(...).save!
Post.first.delete
Post.first.destroy

CassandraStore supports comprehensive query methods in a chainable way:

• all

  Post.all

• where

  Post.where(user: "mrkamel", domain: "example.com")

• where_cql

  Post.where_cql("user = :user", user: "mrkamel")

• limit

  Post.where(...).limit(10)

• order

  Post.where(...).order(id: "asc")

• distinct

  Post.select(:user, :domain).distinct

• select

  Post.select(:user, :domain)

Please note, when using select in the end an array of hashes will be returned instead of an array of Post objects.

• count

  Post.where(...).count

• first

  Post.where(...).first

• find_each

  Post.where(...).find_each(batch_size: 100) do |post|
    # ...
  end

• find_in_batches

  Post.where(...).find_in_batches(batch_size: 100) do |batch|
    # ...
  end

• update_all

  Post.where(...).update_all("message = 'test'")
  Post.where(...).update_all(message: "test")

• delete_all

  Post.where(...).delete_all

Please note, that delete_in_batches will run find_in_batches iteratively and then delete each batch. When dealing with large amounts of records to delete you usually want to use delete_in_batches instead of delete_all, as delete_all can time out.

• delete_in_batches

  Post.where(...).delete_in_batches

Again, please note, that delete_in_batches will run find_in_batches iteratively and then delete each batch. When dealing with large amounts of records to delete you usually want to use delete_in_batches instead of delete_all, as delete_all can time out.

• truncate_table

  Post.truncate_table

Deletes all records from the table. This is much faster than delete_all or delete_in_batches. However, it is not chainable, such that your only option is to remove all records from the table.

CassandraStore is using Semantic Versioning: SemVer

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