Honestly I thought the same as you, then I wrote this, and I now understand it's going to be really hard to do. To make it very simple: there are pointers to query parts "leaking" everywhere across the execution engine. Removing them will require a significant overall of the execution engine, the planner and who knows what else. Even in a single session, two compiled queries will have different compiled code because of that (both llvm and my copyjit have to inject the adresses of various structs in asm code)