Presentation: https://anarazel.de/talks/2018-06-01-pgcon-state-of-jit/state-of-jit.pdf. It mentions “Future things to JIT: Aggregate & Hashjoin hash computation.” I'm not entirely clear where this optimization specifically manifests. I tested tpch-100G. Performance improvements for q5/11 were minimal because expression execution constitutes a very small proportion in these two queries, leaving little room for JIT optimization. Both queries share common hot functions: `ExecParallelScanHashBucket` and `ExecParallelHashJoin`. However, I don't see how these hot functions could be optimized via JIT. I'd appreciate hearing everyone's thoughts.
