True upserts in an append-only world: ReplacingMergeTree and FINAL. Day 07 of the WClickHouse Open-Source Engineering Series. You don't need slow SQL UPDATE statements to maintain current state in ClickHouse. WClickHouse harnesses ReplacingMergeTree for lightning-fast upserts. The Pain Points We Faced Attempting expensive UPDATE mutations on billions of ClickHouse rows Dealing with duplicate state updates in streaming event pipelines Slow analytical queries retur...