‹ BackHN Continuity

Thread

Training a 4B model to produce 81% faster query plans than Postgres

702 points · 144 comments · polyphilz

  1. 2001zhaozhao · · focus · HN ↗
    Engineer: "HELP, our production DB is frozen on this query that worked fine before!"

    Infra: "Hmm, let's check... Well would you look at that, it seems like your LLM query planner usually works and produces fast queries, but this time when you changed a variable name to trigger query rebuild, it happened to hallucinate and miss an index, would you mind re-running the LLM a few times until you get a faster query?"

    1. malisper · · focus · HN ↗
      Funnily enough, you could replace "LLM query planner" with just "query planner" and this comment would still hold true
      1. danielbarla · · focus · HN ↗
        Indeed. I'm honestly shocked that we're still having to evict bad query plans in 2026. And "you changed a variable", ha, that sounds like an actual reason. How about "data statistics were automatically refreshed and you hit some magical undocumented heuristic threshold, an the query that ran in 35ms yesterday now takes 45 minutes. And we can actually tell you this because we have the data, but decided to let you find out manually, instead."

        I've literally been saying "I can't believe the date is X and we still have to put up with this" for around 25 years now.

Open on Hacker News to reply ↗

Unofficial Hacker News client; not affiliated with Y Combinator.