PostHog's 70x faster SQL parser built with Claude Code

Anusheel BhushanAnusheel Bhushanco-founder of PlankOriginally posted on LinkedIn 

Robbie Coomber from PostHog rewrote PostHog's SQL parser using multiple long-running Claude Code sessions in parallel. The result was 16K lines of "hand"-rolled parser code, 5K lines of tooling, a few more K of tests, and a ~70x speed up! Thats awesome. There really is no excuse to not ask Claude or Codex to optimize your codebase. Of course it requires providing the right evals and harness so that it has a way to measure correctness in an objective way.

Also I love that they have a formal declarative grammar for the parser using ANTLR .g4 format.

Read more here: posthog.com/blog/sql-parser

I wrote a 70x faster SQL parser while barely looking at the code - PostHogposthog.com
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