In Cassandra Lunch #91, we will discuss the collection types in Cassandra and how the frozen modifier changes the way that Cassandra interacts with them. Accompanying YouTube: https://youtu.be/z2Fs2TNuuyQ Sign Up For Our Newsletter: http://eepurl.com/grdMkn Join Cassandra Lunch Weekly at 12 PM EST Every Wednesday: https://www.meetup.com/Cassandra-DataStax-DC/events/ Cassandra.Link: https://cassandra.link/ Follow Us and Reach Us At: Anant: https://www.anant.us/ Awesome Cassandra: https://github.com/Anant/awesome-cassandra Cassandra.Lunch: https://github.com/Anant/Cassandra.Lunch Email: solutions@anant.us LinkedIn: https://www.linkedin.com/company/anant/ Twitter: https://twitter.com/anantcorp Eventbrite: https://www.eventbrite.com/o/anant-1072927283 Facebook: https://www.facebook.com/AnantCorp/ Join The Anant Team: https://www.careers.anant.us

1. Version 1.0
Cassandra Collections
Cassandra collections types, the frozen modifier and how
they interact with tombstones.
Obioma Anomnachi
Engineer @ Anant

2. Collection Types
● Collections group and store multiple elements within a single column
○ Similar to Arrays and other data structures in traditional programming languages
● There are three types of collections in Cassandra
○ Set
○ List
○ Map
● There are hard item number limits, as well as item limits to what can be stored in collections
○ Items in a list or map can be up to 2GB, while items in a set can only be up to 64KB
○ The max number of keys in a map is 65,535
○ Only 2 billion items can be queried from a collection
● There are also soft limits to what should be stored in collections
○ Data with potential for unbounded growth shouldn’t be stored in collections
○ When querying collections, the entire collection is read
■ Therefore to avoid performance impacts, keep collections small

3. Set
● A set is a group of unique elements
○ Sets are theoretically unordered, but when queried, returns results in sorted order
● Creation syntax
○ Column_name set<type>
● Interaction syntax
○ Set items are comma separated and contained within curly brackets
○ {element_0, element_1, … element_n}
● All collections have a path and a value, for sets data is stored in the path while the value is left
blank.

4. List
● A list is a group of elements in a specific order. Lists can contain duplicate values.
○ List elements are associated with specific indices and can be retrieved using them
● Creation syntax
○ Column_name list<type>
● Interaction syntax
○ List items are comma separated and contained within square brackets
○ [element_0, element_1, … element_n]
● All collections have a path and a value, for lists data is stored in the value and indices are stored in
the path

5. Maps
● Maps contain elements that are key-value pairs.
○ They are analogous to python dicts or JSON objects
● Creation syntax
○ Column_name map<type_0, type_1>
● Interaction syntax
○ Map elements are comma separated from each other and contained within curly brackets. They key and
value are separated by a colon.
○ {key_0 : value_0, key_1: value_1, …, key_n : value_n}
● Each element of the map acts like a Cassandra column and can be modified, replaced, and deleted

6. Frozen
● Frozen is a modifier that can be added to any collection
○ It causes collection data for individual rows to be stored as the blob type.
○ Without frozen, an update could be made to a particular field within a collection
■ Without it only the entire collection can be overwritten
● Only frozen collections can nest within other collections
● Only frozen collections can be part of a tables primary key
● Creation syntax
○ Column_name frozen<collection_type<collection_value_type(s)>>

7. Demo

8. Resources

9. Strategy: Scalable Fast Data
Architecture: Cassandra, Spark, Kafka
Engineering: Node, Python, JVM,CLR
Operations: Cloud, Container
Rescue: Downtime!! I need help.
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