ANTLR

PostHog engineer Robbie Coomber rebuilt the company's SQL parser using AI agents, replacing an ANTLR-generated parser with a hand-rolled recursive-descent parser that runs 70 times faster. The project…

PostHog engineer rewrote the company's SQL parser using AI agents, achieving a 70x speedup with 16K lines of hand-rolled parser code. The new parser replaces an ANTLR-generated parser and is equivalen…