PostHog’s SQL parser rebuilt to run 70× faster with minimal code changes

A contributor to PostHog set out to improve its built‑in SQL parser. The existing parser was functional but suffered from performance limits. By examining only a small portion of the codebase, the author identified key bottlenecks. A rewrite replaced the core parsing logic with a streamlined implementation. Benchmarks showed the new parser runs roughly 70 times faster than the original. The speed gain reduces query latency for PostHog users. The changes were merged back into the open‑source project. Future work may focus on further optimization and broader testing.