What does Compaction mean in Cassandra?

In Cassandra, Compaction is a process used to merge and clean up SSTable (Sorted String Table) files. As data is written, Cassandra will write it to different SSTable files and periodically execute the Compaction process in the background to merge these files to reduce storage space usage and improve read performance.

The Compaction process can be divided into two types: proactive Compaction and reactive Compaction. Proactive Compaction is a background task automatically performed by Cassandra, which regularly merges and cleans up old SSTable files. Reactive Compaction is a process triggered by Cassandra when reading data, which merges and cleans up data as needed to improve performance.

Using the Compaction process, Cassandra is able to efficiently manage the storage and retrieval of data, ensuring consistency and reliability. Compaction process can also optimize data storage structure, improve read performance, and reduce storage space usage.