I was actually confused by this submission as it puts so much of an emphasis on initial compilation time, when every DB (apparently except for pgsql) caches that result and shares it/reuses it until invalidation. Invalidation can occur for a wide variety of reasons (data composition changing, age, etc), but still the idea of redoing it on every query, where most DBs see the same queries endlessly, is insane.
To make code shareable between processes takes effort and will have tradeoff in performance since it is not specialized to the process.
If the query plan where at least serializable which is more like a AST then at least that part could be reused and then maybe have jitted code in each processes cached in memory that the plan can reference by some key.
DB's like MSSQL avoid the problem because they run a single OS process with multiple threads instead. This is also why it can handle more connections easily since each connection is not a whole process.
"This obvious drawback of the current software architecture motivates our work: sharing JIT code caches across applications. During the exploration of this idea, we have encountered several challenges. First of all, most JIT compilers leverage both runtime context and profile information to generate optimized code. The compiled code may be embedded with runtime-specific pointers, simplified through unique class-hierarchy analysis, or inlined recursively. Each of these "improve- ments" can decrease the shareability of JIT compiled code."
Anythings doable here with enough dev time. Would be nice if PG could just serialize the query plan itself maybe just as an SO along with non-process specific executable code that then has to be dynamically linked again in other processes.
