ClickHouse Deduplicates Retried Inserts: A UInt128 Hash of the Block Plus the Partition ID
ClickHouse hashes each inserted block into a UInt128 dedup token and keeps a bounded window of recent tokens to detect retries.
Clickhouse
ReplacingMergeTree Keeps One Row per Sorting Key: SELECT FINAL Re-runs the Collapse at Query Time
ReplacingMergeTree collapses rows by sorting key and version; SELECT FINAL recomputes that collapse at query time.
ClickHouse's Bloom Filter Skip Index: One 64-Bit Hash, k Fixed Seeds, a 21-by-15 Rate Table
ClickHouse’s bloom_filter skip index keeps one bitset per granule and derives k bit positions from one 64-bit hash.
ClickHouse Deletes Rows With a One-Byte Mask: Wide Parts Hardlink the Rest
ClickHouse’s lightweight DELETE stores a hidden _row_exists mask column and hardlinks every other column instead of rewriting them.
ClickHouse's Window Transform Feeds Only the Rows That Entered the Frame: Three Nested Bounds
ClickHouse’s window transform advances a moving frame and updates the aggregate state incrementally instead of recomputing it per row.