ClickHouse Prunes Granules with a Bloom Filter Skip Index
ClickHouse’s bloom_filter skip index keeps one bitset per granule and derives k bit positions from one 64-bit hash.
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ClickHouse Runs Regular Expressions Four Different Ways
ClickHouse analyses a regexp before running it, and often never runs RE2 at all.
ClickHouse Shares a CPU Budget Between Queries with Fair CPU Slots
ClickHouse shares a global CPU-slot budget between queries with a max-min-fair scheduler, where each query’s slot ceiling is mutable and raised only when the pipeline finds real …
ClickHouse's Hash Join Stores the Right Table as 64-bit Row Words
The ClickHouse hash join keeps the right table as blocks and stores one tagged 64-bit row word per hash-table cell.
ClickHouse's Merge Join Walks Two Sorted Streams and Skips Whole Runs
ClickHouse’s merge join advances two sorted cursors in lockstep and uses a fused compare-and-run-search to skip whole equal-key runs.