Hey, amateur here - but has anybody tried to do a database where your edge servers literally run jit code? Like, you'd define a predicate like an OpenCL kernel, as a small ball of code taking a predetermined set of constants or per-row variables, then presumably push this as LLVM bytecode and let the edges compile it into locally appropriate loops (probably with caching). Is the problem there that it would become hard to apply optimizations that depend on awareness of data structure at a higher-than-row level?

So there are plenty of systems that compile portions of a SQL plan to bytecode (LLVM or JVM) or machine code directly. Usually, the part you compile is the SQL plan and most importantly the predicate filters.

Common operations like networking, transaction management and even index walks (except the key comparisons) are already compiled to native code, so you don't need to go all in. You just optimize the stuff that needs it.