ClickHouse OPTIMIZE TABLE FINAL: When to Use and Avoid

Scheduled OPTIMIZE TABLE FINAL can degrade ClickHouse performance by creating oversized parts that bypass normal merge guardrails. It forces physical rewrites consuming I/O and CPU, and may cause duplicates to reaccumulate. For deduplication, use SELECT FINAL instead, and fix 'too many parts' by batching inserts or using asynchronous inserts.