Cassandra Practice Test

If you have clustering columns defined, what happens to partition key columns?

1. They become unnecessary

2. They are still mandatory

3. They can be combined

4. They are treated as secondary indexes

The correct answer is: They are still mandatory

In a Cassandra database, partition key columns play a crucial role in determining how data is distributed across the nodes in the cluster. They are essential for achieving scalability and performance. When you define clustering columns within a table, the partition key columns remain mandatory because they dictate which partition the data resides in. Every row must belong to a partition defined by the partition key, ensuring that the data is correctly organized and efficiently retrievable. In this context, while clustering columns allow for ordering and querying of data within the same partition, they do not replace or eliminate the requirement for partition keys. Partition keys are fundamental to how Cassandra handles data distribution and are integral to optimizing read and write operations, thereby making them necessary despite the presence of clustering columns.