Is it necessary to update or delete data in ClickHouse, or do they just sit there?

ClickHouse is a columnar analytical database optimized for fast inserts and reading large volumes of data. It does not have traditional UPDATE and DELETE operations as in OLTP databases.

Data in ClickHouse usually "resides" and is not modified after insertion. Special mechanisms are used for updating or deleting data:

• Mutating queries (ALTER UPDATE/DELETE) — introduced in newer versions, but do not work as quickly and efficiently as in traditional DBMS.
• Partitioning and TTL — often used for automatic deletion of old data based on time.
• Data rewriting — if data needs to be updated, a new table with the necessary changes is often created, and links are switched.

Thus, in ClickHouse, data is mainly added, and updates and deletions are rare and circumstantial operations, which are better minimized in the application architecture.