What Is UUID Data Type in Cassandra?
UUID, which stands for Universally Unique Identifier, is a data type in Cassandra that is used to represent a 128-bit value. It is often referred to as a globally unique identifier because the chances of generating two identical UUIDs are extremely low.
Why Use UUIDs?
The primary reason for using UUIDs in Cassandra is their uniqueness. Unlike other identifiers such as auto-incrementing integers or timestamps, UUIDs provide a guarantee that they will not collide with any other identifier generated within the system.
In distributed systems like Cassandra, where data is stored on multiple nodes across different geographic locations, maintaining uniqueness becomes even more critical. UUIDs enable easy and conflict-free merging of data from multiple sources without the need for centralized coordination.
How Are UUIDs Generated?
Cassandra supports two types of UUID generation:
- Type 1: Time-based UUID
- Type 4: Randomly generated UUID
Type 1: Time-based UUID
A time-based UUID combines the timestamp of its generation with the MAC address (media access control) of the machine generating it. This type provides some ordering guarantees and can be useful when sorting or querying data based on creation time.
Type 4: Randomly Generated UUID
A randomly generated UUID uses random numbers or pseudo-random numbers to create a unique identifier. This type does not rely on any specific information from the system and provides an equal probability of occurrence for each possible value.
Using UUID Data Type in Cassandra
In Cassandra, you can define a column or field to have the UUID data type. This allows you to store and manipulate UUID values directly in your tables.
Here’s an example of how to create a table with a UUID column:
CREATE TABLE users ( user_id UUID PRIMARY KEY, name text, email text );
You can then insert values into the table using valid UUIDs:
INSERT INTO users (user_id, name, email) VALUES (uuid(), 'John Doe', 'email@example.com');
And retrieve data using UUIDs as well:
SELECT * FROM users WHERE user_id = 550e8400-e29b-41d4-a716-446655440000;
UUIDs are a powerful and widely used data type in Cassandra. They provide uniqueness guarantees and enable conflict-free merging of distributed data. By incorporating the UUID data type into your Cassandra schema, you can ensure the integrity and reliability of your data in a distributed environment.