How we made WINDOW JOIN parallel and vectorized
Summary
This article explains QuestDB's WINDOW JOIN feature, detailing how a dedicated window-join operator, data-level parallelism, and SIMD-accelerated aggregation deliver large speedups for time-series workloads. It compares the window-join approach with traditional ASOF/RANGE joins, describes the frame-based parallelism and per-key buffering path, and presents benchmark results showing significant gains over single-threaded plans and other databases.