How we made WINDOW JOIN parallel and vectorized (opens in new tab)

WINDOW JOIN is QuestDB's dedicated syntax for aggregating one table over a time window around each row of another. We parallelized it across page frames, used a low-cardinality join key to unlock a vectorized aggregation path, and benchmarked it against Timescale, DuckDB, and ClickHouse on a 50M x 150M row workload.