[masklinn]

Yeah pg’s JIT is a pretty good demonstration that LLVM is not great at JITs, worsened by postgres not having a good persistent shared query cache.

It would probably be less detrimental if it could perform asynchronous compilation for future queries (which really is closer to how normal JITs actually behave, at least for optimising backends)

[MaxBarraclough]

> LLVM is not great at JITs

That seems like a generalisation. It's true LLVM will never be a lightweight toolkit, but if you want to generate highly optimised code it seems like a solid choice, assuming you're doing relatively 'vanilla' code-gen work.

[SigmundA]

PG just needs to do like the other databases and cache query plans, also add hints please.

[masklinn]

> PG just needs to do like the other databases and cache query plans

The inline blocking compilation step will still fuck your query.

> also add hints please

I’d much rather they allowed bypassing the planner entirely and had an interface to feed plans directly to the executor.

[RMarcus]

PostgreSQL has coarse-grain query hints (like `enable_hashjoin`), and the excellent `pg_hint_plan` extension allows you to specify a complete or partial execution plan: https://github.com/ossc-db/pg_hint_plan

[SigmundA]

>The inline blocking compilation step will still fuck your query

Only on the first execution, the long plan/jit time is usually only an issue when running a fast query over and over again.

However if plans where cached then you could also plan without jitting then background jit and update cached plan for next time which would be even smarter.

>I’d much rather they allowed bypassing the planner entirely and had an interface to feed plans directly to the executor

Other database have plan locking where you can load an existing plan from somewhere else in serialized form (XML) and force it to use that. Most of the time I prefer just a few hints in the query source solves almost all issue with the planner.