For one of my personal projects I am interested in using the PostgreSQL planner as a standalone library. However, I would like to run this as an embedded library instead of actually creating anything on disk.
I've realized that postgres has several pg_operator, pg_class etc. tables which it uses for query planning purposes. Is there any PostgreSQL component interface whose implementation could be overridden to not actually try to read these tables from disk but instead read it from a custom memory region that is managed by my code.