My Rust as-of join is slower than Polars
TL;DR. In March 2026 I published a README table saying my Rust as-of join, FlowState, was 1.8 times faster than Polars (10 ms against 18 ms)1. When I wrote a reproducible benchmark in October, the result reversed: in my runs on one Apple M4 laptop FlowState’s median was 13.3 ms against 9.9 ms for Polars on 1M left rows23, and 194.9 ms against 135.8 ms on 10M left rows45. I removed the March claim. Rebuilding the March kernel did not bring the lead back6, and I do not know why Polars is faster or what produced the original number. ...