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.
Joins
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.