hckrnws

> However, standard LLVM-based JIT is notoriously slow at compilation. When it takes tens to hundreds of milliseconds, it may be suitable only for very heavy, OLAP-style queries, in some cases.

I don't know anything here, but this seems like a good case for ahead of time compilation? Or at least caching your JIT results? I can image much of the time, you are getting more or less the same query again and again?

Yes.

Some years ago we ported some code from querying out the data and tallying in Python (how many are in each bucket) to using SQL to do that. It didn't speed up the execution. I was surprised by that, but I guess the Postgres interpreter is roughly the same speed as Python, which when you think about it perhaps isn't that surprising.

But Python is truly general purpose while the core query stuff in SQL is really specialized (we were not using stored procedures). So if Pypy can get 5x speedup, it seems to me that it should be possible to get the same kind of speed up in Postgres. I guess it needs funding and someone as smart as the Pypy people.

The last time I looked into it my impression was that disabling the JIT in PostgreSQL was the better default choice. I had a massive slowdown in some queries, and that doesn't seem to be an entirely unusual experience. It does not seem worth it to me to add such a large variability to query performance by default. The JIT seemed like something that could be useful if you benchmark the effect on your actual queries, but not as a default for everyone.

That is quite strange, given that big boys RDMS (Oracle, SQL Server, DB2, Informix,...) all have JIT capabilities for several decades now.

awesome! I wonder if it's possible to point AI at this problem and synthesize a bespoke compiler (per-architecture?) for postgresql expressions?

Two things are holding back current LLM-style AI of being of value here:

* Latency. LLM responses are measured in order of 1000s of milliseconds, where this project targets 10s of milliseconds, that's off by almost two orders of magnitute.

* Determinism. LLMs are inherently non-deterministic. Even with temperature=0, slight variations of the input lead to major changes in output. You really don't want your DB to be non-deterministic, ever.

The suggestion was not to use an LLM to compile the expression, but to use an LLM to build the compiler.

> 1000s of milliseconds

Better known as "seconds"...