The document provides an introduction to Cassandra, describing it as a distributed, non-relational, and linearly scalable database management system that is aware of multiple data centers. It then demonstrates Cassandra's data model and terminology, showing how data is organized into clusters, keyspaces, tables, rows, columns, and values. Indexing techniques are also briefly discussed.

1. Cassandra
A short Intro
Vitaly Kushner
astrails.com

2. • Distributed
• Non-relational
• Linearly scalable
• Multi data-center aware

3. BigTable
http://labs.google.com/papers/bigtable.html

4. Terminology Sucks
big time

5. my_cluster: {
demo_app: {
accounts: {
"1": {
"attributes": {
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

6. my_cluster: { <<= Cluster Name
demo_app: {
accounts: {
"1": {
"attributes": {
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

7. my_cluster: {
demo_app: { <== Keyspace
accounts: {
"1": {
"attributes": {
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

8. my_cluster: {
demo_app: {
accounts: { <<= super column family
"1": {
"attributes": {
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

9. my_cluster: {
demo_app: {
accounts: {
"1": {
"attributes": {
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: { <<= column family
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

10. my_cluster: {
demo_app: {
accounts: {
"1": { <<= key
"attributes": {
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

11. my_cluster: {
demo_app: {
accounts: {
"1": {
"attributes": { << super column
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

12. my_cluster: {
demo_app: {
accounts: {
"1": {
"attributes": {
"name": "astrails" <<= column
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

13. my_cluster: {
demo_app: {
accounts: {
"1": {
"attributes": {
"name": "astrails" <<= value
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly",
"email": "vitaly@astrails.com"
}
}
}
}

14. my_cluster: {
demo_app: {
accounts: {
"1": {
"attributes": {
"name": "astrails"
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: {
"1": {
"name": "vitaly", <<= column
"email": "vitaly@astrails.com"
}
}
}
}

15. my_cluster: { <<= cluster
demo_app: { <<= keyspace
accounts: { <<= super column family
"1": { <<= key
"attributes": { <<= supercolumn
"name": "astrails" <<= column
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: { <<= column family
"1": { <<= key
"name": "vitaly", <<= column
"email": "vitaly@astrails.com"
}
}
}
}

16. my_cluster: { <<= cluster
demo_app: { <<= database
accounts: { <<= super column family
"1": { <<= key
"attributes": { <<= supercolumn
"name": "astrails" <<= column
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: { <<= column family
"1": { <<= key
"name": "vitaly", <<= column
"email": "vitaly@astrails.com"
}
}
}
}

17. my_cluster: { <<= cluster
demo_app: { <<= database
accounts: { <<= table
"1": { <<= key
"attributes": { <<= supercolumn
"name": "astrails" <<= column
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: { <<= column family
"1": { <<= key
"name": "vitaly", <<= column
"email": "vitaly@astrails.com"
}
}
}
}

18. my_cluster: { <<= cluster
demo_app: { <<= database
accounts: { <<= table
"1": { <<= key
"attributes": { <<= supercolumn
"name": "astrails" <<= column
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: { <<= table
"1": { <<= key
"name": "vitaly", <<= column
"email": "vitaly@astrails.com"
}
}
}
}

19. my_cluster: { <<= cluster
demo_app: { <<= database
accounts: { <<= table
"1": { <<= key
"attributes": { <<= collection
"name": "astrails" <<= column
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: { <<= table
"1": { <<= key
"name": "vitaly", <<= column
"email": "vitaly@astrails.com"
}
}
}
}

20. my_cluster: { <<= cluster
demo_app: { <<= database
accounts: { <<= table
"1": { <<= key
"attributes": { <<= collection
"name": "astrails" <<= attribute
},
"users": {
"1" => "",
"3" => "",
}
}
},
users: { <<= table
"1": { <<= key
"name": "vitaly", <<= attribute
"email": "vitaly@astrails.com"
}
}
}
}

21. Indexing

22. "my_cluster": {
"demo_app": {
"users": {
"b2c75e99-e079-449d-b562-293dfdbf006e": {
"attributes": {
"name": "Vitaly",
"email": "vitaly@astrails.com",
"remember_me": "74c4f3a2c85b66f216211edd5245d25ba251d83e"
}
}
},
"emails": {
"vitaly@astrails.com": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
"remember_me": {
"74c4f3a2c85b66f216211edd5245d25ba251d83e": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
}
}

23. "my_cluster": {
"demo_app": {
"users": {
"b2c75e99-e079-449d-b562-293dfdbf006e": {
"attributes": {
"name": "Vitaly",
"email": "vitaly@astrails.com",
"remember_me": "74c4f3a2c85b66f216211edd5245d25ba251d83e"
}
}
},
"emails": {
"vitaly@astrails.com": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
"remember_me": {
"74c4f3a2c85b66f216211edd5245d25ba251d83e": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
}
}

24. "my_cluster": {
"demo_app": {
"users": {
"b2c75e99-e079-449d-b562-293dfdbf006e": {
"attributes": {
"name": "Vitaly",
"email": "vitaly@astrails.com",
"remember_me": "74c4f3a2c85b66f216211edd5245d25ba251d83e"
}
}
},
"emails": {
"vitaly@astrails.com": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
"remember_me": {
"74c4f3a2c85b66f216211edd5245d25ba251d83e": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
}
}

25. "my_cluster": {
"demo_app": {
"users": {
"b2c75e99-e079-449d-b562-293dfdbf006e": {
"attributes": {
"name": "Vitaly",
"email": "vitaly@astrails.com",
"remember_me": "74c4f3a2c85b66f216211edd5245d25ba251d83e"
}
}
},
"emails": {
"vitaly@astrails.com": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
"remember_me": {
"74c4f3a2c85b66f216211edd5245d25ba251d83e": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
}
}

26. "my_cluster": {
"demo_app": {
"users": {
"b2c75e99-e079-449d-b562-293dfdbf006e": {
"attributes": {
"name": "Vitaly",
"email": "vitaly@astrails.com",
"remember_me": "74c4f3a2c85b66f216211edd5245d25ba251d83e"
}
}
},
"emails": {
"vitaly@astrails.com": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
"remember_me": {
"74c4f3a2c85b66f216211edd5245d25ba251d83e": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
}
}

27. "my_cluster": {
"demo_app": {
"users": {
"b2c75e99-e079-449d-b562-293dfdbf006e": {
"attributes": {
"name": "Vitaly",
"email": "vitaly@astrails.com",
"remember_me": "74c4f3a2c85b66f216211edd5245d25ba251d83e"
}
}
},
"emails": {
"vitaly@astrails.com": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
"remember_me": {
"74c4f3a2c85b66f216211edd5245d25ba251d83e": "b2c75e99-e079-449d-b562-293dfdbf006e",
}
}
}

28. Playtime

29. > gem install cassandra
...
> cassandra_helper cassandra
...

30. <ClusterName>my_cluster</ClusterName>
<Keyspaces>
<Keyspace Name="demo_app">
<ColumnFamily CompareWith="UTF8Type" Name="users" ColumnType="Super" CompareSubcolumnsWith="UTF8Type" />
<ColumnFamily CompareWith="UTF8Type" Name="emails" ColumnType="Super" CompareSubcolumnsWith="UTF8Type" />
<ColumnFamily CompareWith="UTF8Type" Name="tokens" />
</Keyspace>
</Keyspaces>

31. require 'rubygems'
require 'cassandra'
include Cassandra::Constants
client = Cassandra.new('demo_app')
client.insert(:users, "1", {"name" => "vitaly", "email" => "vitaly@astrails.com"})
client.insert(:accounts, "1", {"attributes" => {"name" => "astrails"}, "users" => {"1" => ""}})
client.insert(:users, "2", {"name" => "boris"})
client.insert(:accounts, "1", {"users" => {"2" => ""}})
client.get(:users, "1")

32. Rails?

33. YES!

34. SmallRecord
WARNING: waporware :)

35. http://github.com/astrails/small_record

36. ActiveModel

37. class Account < SmallRecord::Base
attribute :name
attribute :created_at, :type => :datetime
has_many :users
validates_presence_of :name
end
class User < SmallRecord::Base
attribute :name
attribute :email
attribute :created_at, :type => :datetime
attribute :account_id
def account
@account ||= Account.find(:account_id)
end
validates_presence_of :name
validates_presence_of :email
end
Account.find(params[:account]).users.first.name

38. production:
adapter: cassandra
host: 127.0.0.1
port: 9160
keyspace: chronos
development:
adapter: mock
test:
adapter: mock

39. production:
adapter: cassandra
host: 127.0.0.1
port: 9160
keyspace: chronos
development:
adapter: mock
test:
adapter: mock

40. Some Links
• http://incubator.apache.org/cassandra
• http://labs.google.com/papers/bigtable.html
• http://blog.evanweaver.com/articles/2009/07/06/up-and-running-with-cassandra/
• http://arin.me/blog/wtf-is-a-supercolumn-cassandra-data-model
• http://github.com/astrails/small_record