Before scanning a relation, in the planner stage, I want to make a call to retrieve information about how many pages will be a hit for a specific relation. The module pg_buffercache seems to be doing a similar thing. Also, pg_statio_all_tables seems to be having that information, but it is updated after execution. However, I want the information before execution. Also not sure how pg_statio_all_tables is created and how I can access it in the code.
